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See detailSensitivity to Convective Schemes on Precipitation Simulated by the Regional Climate Model MAR over Belgium (1987–2017)
Doutreloup, Sébastien; Wyard, Coraline; Amory, Charles; Kittel, Christoph; Erpicum, Michel; Fettweis, Xavier

in Atmosphere (2019), 10(1), 34

The aim of this study is to assess the sensitivity of convective precipitation modelled by the regional climate model MAR (Modèle Atmosphérique Régional) over 1987–2017 to four newly implemented convective schemes: the Bechtold scheme coming from the MESO-NH regional model and the Betts-Miller-Janjić, Kain-Fritsch and modified Tiedtke schemes coming from the WRF regional model. MAR version 3.9 is used here at a resolution of 10 km over a domain covering Belgium using the ERA-Interim reanalysis as forcing. The simulated precipitation is compared against SYNOP and E-OBS gridded precipitation data. Trends in total and convective precipitation over 1987–2017 are discussed. None of the MAR experiments compares better with observations than the others and they all show the same trends in (extreme) precipitation. Over the period 1987–2017, MAR suggests a significant increase in the mean annual precipitation amount over the North Sea but a significant decrease over High Belgium.

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See detailPotential new sources of hypoglycin A poisoning for equids kept at pasture in spring: a field pilot study
Votion, Dominique; Habyarimana, J.A.; Scippo, Marie-Louise; Richard, E.; Marcillaud-Pitel, C.; Erpicum, Michel; Gustin, Pascal

in Veterinary Record: Journal of the British Veterinary Association (2019)

The first objective of this pilot study was to measure the concentration of HGA in samaras of sycamore trees fallen on the ground and then in seedlings from germination. The subsequent objective was to examine other possible sources of HGA intoxication.

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See detailThe climate of Belgium and Luxembourg
Erpicum, Michel; Nouri, Myriem; Demoulin, Alain

in Demoulin, Alain (Ed.) Landscapes and landforms of Belgium and Luxembourg (2018)

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See detailSunlight irradiance and habituation of visual evoked potentials in migraine: The environment makes its mark
Lisicki Martinez, Marco; D'Ostilio, Kevin; Erpicum, Michel; SCHOENEN, Jean; MAGIS, Delphine

in Cephalalgia (2017)

Background Migraine is a complex multifactorial disease that arises from the interaction between a genetic predisposition and an enabling environment. Habituation is considered as a fundamental adaptive behaviour of the nervous system that is often impaired in migraine populations. Given that migraineurs are hypersensitive to light, and that light deprivation is able to induce functional changes in the visual cortex recognizable through visual evoked potentials habituation testing, we hypothesized that regional sunlight irradiance levels could influence the results of visual evoked potentials habituation studies performed in different locations worldwide. Methods We searched the literature for visual evoked potentials habituation studies comparing healthy volunteers and episodic migraine patients and correlated their results with levels of local solar radiation. Results After reviewing the literature, 26 studies involving 1291 participants matched our inclusion criteria. Deficient visual evoked potentials habituation in episodic migraine patients was reported in 19 studies. Mean yearly sunlight irradiance was significantly higher in locations of studies reporting deficient habituation. Correlation analyses suggested that visual evoked potentials habituation decreases with increasing sunlight irradiance in migraine without aura patients. Conclusion Results from this hypothesis generating analysis suggest that variations in sunlight irradiance may induce adaptive modifications in visual processing systems that could be reflected in visual evoked potentials habituation, and thus partially account for the difference in results between studies performed in geographically distant centers. Other causal factors such as genetic differences could also play a role, and therefore well-designed prospective trials are warranted.

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See detailRECONSTRUCTION DE L'ÉVOLUTION DU RAYONNEMENT SOLAIRE REÇU EN SURFACE EN EUROPE OCCIDENTALE SUR LA PÉRIODE 1900-2014 À L'AIDE DU MODÈLE ATMOSPHÉRIQUE RÉGIONAL MAR
Wyard, Coraline; Fettweis, Xavier; Belleflamme, Alexandre; Doutreloup, Sébastien; Erpicum, Michel

in Dahech, Salem; Charfi, Sami (Eds.) Actes du XXXe colloque de l'Association Internationale de Climatologie : Climat, ville et environnement (2017, July)

Many studies show that the surface solar radiation has underwent large variations over the second half of the 20th century as a result of variations in cloud cover and aerosol loading in the atmosphere. However, it is difficult to build strong conclusions before the 1950' because of the observations scarcity. The evolution of the surface solar radiation has been reconstructed over 1900-2014 using the regional model MAR (« Modèle Atmosphérique Régional ») in Belgium. Boundary conditions were provided by four reanalysis products : the ERA-interim (1979-2014) completed by the ERA40 (1958-1978), the NCEP/NCAR-v1 (1948-2014), the ERA-20C (1900-2010) and the 20CRV2C (1900-2010). Results show that the reanalyses can generate divergent trends while they assimilate observations and are supposed to represent the same climate.

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See detailÉvolution de l'enneigement moyen dans les Alpes au cours du 20e siècle à l'aide du modèle atmosphérique régional MAR
Belleflamme, Alexandre; Wyard, Coraline; Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

in Dahech, Salem; Charfi, Sami (Eds.) Actes du XXXème colloque de l'Association Internationale de Climatologie - Climat, ville et environnement (2017, July)

The evolution of the snow height over the Alps can strongly impact tourism, but also the water availability of the region. In this study, we have reproduced the evolution of the climate in the Alps over the 20th century with the help of the regional atmospheric model MAR forced by three reanalyses (ERA-20C, NCEP/NCAR, and ERA-Interim). MAR shows that the snow height has increased since the beginning of the 20th century, first only at higher altitudes, then also at lower levels, before knowing a strong and abrupt decrease between 1985 and 1990. This evolution, which is consistent with observations given in the literature, is directly linked with the trends of NAO and AO. In fact, the atmospheric circulation changes highlighted by NAO and AO induce temperature and precipitation changes that directly determine the snow height in the Alps.

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See detailÉvaluation de la capacité du Modèle Atmosphérique Régional (MAR) à simuler la saison des pluies en Afrique Intertropicale
Doutreloup, Sébastien; Wyard, Coraline; Belleflamme, Alexandre; François, Louis; Fettweis, Xavier; Erpicum, Michel

in Dahech, Salem; Charfi, Sami (Eds.) Actes du XXXe colloque de l'Association Internationale de Climatologie : CLIMAT, VILLE ET ENVIRONNEMENT (2017, July)

In Intertropical Africa, climate is essentially characterized by the amount of precipitation and its annual regime. These precipitations and their evolution during the period 1970-1999 are simulated thanks to the Regional Atmospheric Model (MAR), developed at the ULg, and forced by the NCEP1 reanalyses and by the outputs of three global models (GCM) of the CMIP5 database. These MAR simulations are compared to the gridded data of the Climate Research Unit (CRU). It is clear from our investigations that the simulation of the MAR model forced by the NCEP1 reanalyses is better reproducing the quantities as well as the annual rainfall regime in the semi-arid regions than in equatorial regions. On the other hand, simulations of the MAR forced by the outputs of the GCMs are globally unsatisfactory throughout the intertropical domain in terms of quantities as well as the seasonality of precipitation.

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See detailVery high resolution surface mass balance over Greenland modeled by the regional climate model MAR with a downscaling technique
Kittel, Christoph; Lang, Charlotte; Agosta, Cécile; Prignon, Maxime; Fettweis, Xavier; Erpicum, Michel

Poster (2016, April 20)

This study presents surface mass balance (SMB) results at 10 km resolution with the regional climate MAR model over the Greenland ice sheet. Here, we use the last MAR version (v3.6) where the land-ice module (SISVAT) using a high resolution grid (10km) for surface variables is fully coupled while the MAR atmospheric module running at a lower resolution of 20km. This online downscaling technique enables to correct near-surface temperature and humidity from MAR by a gradient based on elevation before forcing SISVAT. The 20 km precipitations are not corrected. Corrections are stronger over the ablation zone where topography presents more variations. The model has been force by ERA-Interim between 1979 and 2014. We will show the advantages of using an online SMB downscaling technique in respect to an offline downscaling extrapolation based on local SMB vertical gradients. Results at 10 km show a better agreement with the PROMICE surface mass balance data base than the extrapolated 20 km MAR SMB results.

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See detailDOES REGIONAL SOLAR RADIATION INFLUENCE HABITUATION OF VISUAL EVOKED POTENTIALS IN MIGRAINE? A TENTATIVE HYPOTHESIS BASED ON RETROSPECTIVE LITERATURE ANALYSIS
Lisicki Martinez, Marco; D'Ostilio, Kevin; NONIS, Romain; Erpicum, Michel; SCHOENEN, Jean; MAGIS, Delphine

in Cephalalgia (2016), 36(1S), 57

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See detailSnow cover evolution and its impact on flooding in the Ourthe River catchment (southeast of Belgium) over the period 1958­-2014 using the MAR model
Wyard, Coraline; Fettweis, Xavier; Erpicum, Michel

Conference (2015, November 13)

The Ourthe River (southeast of Belgium) is one of the main tributaries of the Meuse River with a catchment area of 3500 km². About 50 % of the floods which occur in the Ourthe River catchment are due to rainfall events associated with the melting of the snow which covers the Ardennes in winter. In this study, hydroclimatic conditions favourable to flooding were reconstructed over the period 1958-2014 using the regional climate model MAR (« Modèle Atmosphérique Régional ») forced by the ERA-interim reanalysis and by the NCEP1 reanalysis. As validation, the MAR results were compared to weather station-based data. A trends analysis was then performed in order to study the evolution of conditions favourable to flooding in the Ourthe River catchment. When the MAR model is forced by the NCEP1 reanalysis, results show a significant decrease in hydroclimatic conditions favourable to flooding because of a decrease in snow accumulation as well as a decrease in the frequency of extreme precipitation events in winter. When MAR is forced by the ERA-interim reanalysis, non-significant trends are found, which could be explained by an underestimation of the precipitation amount computed by the ERA-40 reanalysis before 1979. Further studies are needed to explain the decreasing trends in snow accumulation and extreme precipitation events. Moreover, an hydrological model could also be forced by the MAR outputs in order to improve flood detection.

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See detailEtude de l'évolution de l'enneigement dans les Hautes Fagnes (Belgique) au cours des cinquante dernières années à l'aide du modèle climatique régional MAR
Wyard, Coraline; Fettweis, Xavier; Erpicum, Michel

in Erpicum, Michel (Ed.) Actes du XXVIIIe colloque annuel de l’Association Internationale de Climatologie : Modélisations et variabilités (2015, July)

The “Modèle Atmosphérique Régionale” MAR is a regional climate model originally developed to study the polar ice sheets. In this study, the MAR model has been adapted to Belgium in order to study the snow cover evolution of the High Fens (east of Belgium), a region covered by snow on average one to two months per year. As validation, we have sucessfully compared MAR based daily snow heights with snowcam-based and/or laser sensor-based observations over the period 2008-2013. Then, the model has been forced by ERA-Interim since 1958 to study the snow cover evolution during the last fifty years at the summit of Belgium. The results show no significant trend despite global warming.

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See detailFuture climate and surface mass balance of Svalbard glaciers in an RCP8.5 climate scenario: a study with the regional climate model MAR forced by MIROC5
Lang, Charlotte; Fettweis, Xavier; Erpicum, Michel

in Cryosphere (2015), 9

We simulated the 21st century Svalbard SMB with the regional model MAR (RCP8.5 scenario). Melt is projected to increase gently up to 2050 and then dramatically increase, with a larger increase in the south of the archipelago. This difference is due to larger ice albedo decrease in the south causing larger increase of absorbed solar radiation. The ablation area is projected to disappear over the entire Svalbard by 2085. The SMB decrease compared to present is projected to contribute 7mm to SLR.

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See detailGlobal, diffuse and direct irradiances modelling over northwestern Europe using regional climate model MAR : validation and construction of a 30-year climatology
Beaumet, Julien; Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

Poster (2015, April 17)

Incoming solar global irradiances are modelled using MAR regional climate model forced by ERA-Interim reanalysis. Global irradiances are decomposed into direct and diffuse using sigmoid model from Ruiz-Arias et al. (2010). Results are validated using data from the European Solar Radiation Atlas for Uccle and Braunschweig weather stations. A 30-year climatology has been built and trends and variability have been analyzed.

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See detailSnow cover evolution during the last fifty years in the Hautes Fagnes (Belgium) using the regional climate MAR model
Wyard, Coraline; Fettweis, Xavier; Erpicum, Michel

Conference (2015, April 16)

The MAR model is a regional climate model originally developped for the polar regions to study the surface mass balance. In this study, the MAR model has been adapted to Belgium in order to study the snow cover evolution of the Hautes Fagnes (south-east of Belgium), a region covered by snow one to two months per year. As validation, we have sucessfully compared MAR based daily snow heights with snowcam-based observations. Then, the model has been forced by ERA-Interim since 1958 to study the snow cover evolution during the last fifty years at the summit of Belgium. The results show non-significant trend.

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See detailRecent summer Arctic atmospheric circulation anomalies in a historical perspective
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

in Cryosphere (2015), 9

A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from five reanalysis data sets (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.

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See detailStable climate and surface mass balance in Svalbard over 1979–2013 despite the Arctic warming
Lang, Charlotte; Fettweis, Xavier; Erpicum, Michel

in Cryosphere (2015), 9

With the help of the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-Interim reanalysis (MARERA) and the MIROC5 (Model for Interdisciplinary Research on Climate) global model (MARMIROC5) from the CMIP5 (Coupled Model Intercomparison Project) database, we have modelled the climate and surface mass balance of Svalbard at a 10 km resolution over 1979–2013. The integrated total surface mass balance (SMB) over Svalbard modelled by MARERA is negative (−1.6 Gt yr−1) with a large interannual variability (7.1 Gt) but, unlike over Greenland, there has been no acceleration of the surface melt over the past 35 years because of the recent change in atmospheric circulation bringing northwesterly flows in summer over Svalbard, contrasting the recent observed Arctic warming. However, in 2013, the atmospheric circulation changed to a south–southwesterly flow over Svalbard causing record melt, SMB (−20.4 Gt yr−1) and summer temperature. MIROC5 is significantly colder than ERA-Interim over 1980–2005 but MARMIROC5 is able to improve the near-surface MIROC5 results by simulating not significant SMB differences with MARERA over 1980–2005. On the other hand, MIROC5 does not represent the recent atmospheric circulation shift in summer and induces in MARMIROC5 a significant trend of decreasing SMB (−0.6 Gt yr−2) over 1980–2005.

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See detailPhotosynthesis of Scenedesmus obliquus in outdoor open thin-layer cascade system in high and low CO2 in Belgium
de Marchin, Thomas; Erpicum, Michel; Franck, Fabrice

in Journal of Biotechnology (2015), 215

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See detailSensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR
Noel, Brice; Fettweis, Xavier; van de Berg, W.J.; van den Broeke, M.R.; Erpicum, Michel

in Cryosphere (2014), 8

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North Atlantic Oscillation (NAO), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS.

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See detailSolar irradiance modelling over Belgium using Regional Climate Models within the frame of a day-ahead photovoltaic production forecasting system
Beaumet, Julien; Doutreloup, Sébastien; Fettweis, Xavier; Hermans, Aline; Erpicum, Michel

Poster (2014, October 06)

WRF-ARW and MAR climate models performances for the modelling of solar irradiances over Belgium are evaluated using in-situ measurements at Sart-Tilman and Daussoulx. Different WRF-ARW settings are tested. Sigmoid model proposed by Ruis-Ariaz etal. (2010) is used to decompose solar irradiance into direct and diffuse fraction. The performance of this model using measured and modelled global irradiances is also evaluated.

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See detailPhotosynthetic adaptations during cultivation of Scenedesmus in open thin-layer cascade system in Liège
de Marchin, Thomas; Erpicum, Michel; Franck, Fabrice

Conference (2014, September 24)

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See detailComparaison entre le profil vertical de la vitesse du vent observé dans les basses couches de la troposphère et celui simulé par le modèle WRF en Belgique
Doutreloup, Sébastien; Fettweis, Xavier; Beaumet, Julien; Erpicum, Michel

in Camberlin, Pierre; Richard, Yves (Eds.) Actes du XXVIIe Colloque de l'Association Internationale de Climatologie : CLIMAT : SYSTÈME & INTERACTIONS (2014, July 02)

In the framework of FLEXIPAC project funded by the "RELIABLE" program of Walloon Region (Belgium), the Laboratory of Climatology Topoclimatology (LCT) of the University of Liège (Belgium) aims to adjust the WRF regional model (v.3.4.) forced by the ERA-Interim reanalysis for Belgium. Our analysis shows that wind speeds at 100m simulated by WRF are systematically overestimated compared to wind speeds extracted from wind productions of two wind farms. In order to solve this problem, four ways are considered in this contribution. The first way is to compare the WRF model with the reanalysis data. The second way is to test the influence of the spatial resolution by running WRF with a finer resolution. The third way is to smooth WRF outputs, where in order to analyze the variability created by the model. And finally, the fourth way is to compare the WRF model with the MAR (v3.3.) regional model. This last way seems to confirm that the MAR model better simulates wind speeds at 10m and at 100m than the WRF model.

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See detailMICROPHYSIQUE DES NUAGES ET RAYONNEMENT SOLAIRE : COMPARAISON DES MESURES IN SITU AU MONT RIGI EN HAUTE BELGIQUE ET DES DONNÉES CLOUD PHYSICAL PROPERTIES (CPP) OBTENUES À PARTIR DES IMAGES METEOSAT-9
Beaumet, Julien; Clerbaux, Nicolas; Cornet, Yves; Fettweis, Xavier; Erpicum, Michel

in Camberlin, Pierre; Richard, Yves (Eds.) Actes du XXVIIe Colloque de l'Association Internationale de Climatologie : CLIMAT : SYSTÈME & INTERACTIONS (2014, July 02)

Le rayonnement solaire global mesuré au mont Rigi a été comparé à l'épaisseur optique des nuages (COT) estimée à l'aide des données SEVIRI. Une relation logarithmique avec un coefficient de détermination d'environ 0,5 a été trouvée. Ce résultat plutôt faible peut en grande partie s'expliquer par un nombre limité de cas où subsistent des erreurs de positionnement ou par des interactions plus complexes entre nébulosité et rayonnement. De plus, l'incertitude sur l'estimation de l'épaisseur optique des nuages à l'aide des données SEVIRI pour les nuages optiquement plus épais n'est pas négligeable.

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See detailSolar irradiance modelling over Belgium using WRF-ARW : A sensitivity analysis of Mellor-Yamada-Nakanishi-Niino (BYNN) boundary layer scheme parameters
Beaumet, Julien; Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

Conference (2014, June 06)

Global solar irradiances at ground level are modelled over Belgium using latest version of WRF-ARW regional climate model (RCM). The model set-up used has a resolution of 5 kilometres. The boundary layer scheme chosen is the Mellor-Yamada-Nakanishi-Niino (MYNN) 2.5 scheme with the Turbulent Kinetic Energy (TKE) closure proposed by Canuto et al., (2008) and Kitamura (2010). In this scheme, the modification of some parameters allows to change the determinant mixing length (surface layer, planet boundary layer, top of boundary layer/entrainment) which then modifies heat and moistures fluxes produced by turbulent mixing. Such modifications have significant influences on modelled cloudiness and therefore on modelled global solar irradiance incoming at the surface. The present study proposes a sensitivity analysis of the different parameters that influence the mixing length ('alp1' to 'alp5') and the TKE diffusion ('Sqfac') in order to find the most suitable constant values of these parameters for the modelling of cloudiness over Belgium. Results of different simulations are compared with global solar irradiance measurements performed by the Centre Spatial de Liège at Sart-Tilman in 2013 and 2014. Firsts results show that the dry bias frequently found when using WRF-ARW with standard set-ups can be greatly reduced thanks to an increased modelled cloudiness. The quantitative and qualitative effects of these modifications over cloudiness are also analysed by displaying 2D representation of modelled clouds over Sart-Tilman and confronting them with on-site observations.

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See detailComparison between wind speed observed at 100m height and wind speeds simulated by the WRF and MAR models
Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel; Breuer, Christophe; Beaumet, Julien

Poster (2014, June 06)

In the context of FLEXIPAC project funded by "RELIABLE" program of Walloon Region (Belgium), the Laboratory of Climatology and Topoclimatology (LCT) of the University of Liège (Belgium) aims to adjust the WRF regional model (v.3.4.) forced by ERA-Interim model. Our analysis shows that wind speeds at 100m height simulated by WRF are systematically overestimated compared to wind speeds extracted from wind productions of two wind farms. In order to identify this problem, four comparisons were performed in this contribution. Firstly, we compare WRF model with reanalysis based forcing model. Secondly, we compare two WRF simulations, where one of them has a more precise spatial resolution. Thirdly, we smooth WRF outputs in time (6-hr running mean) in order to study the accuracy of the 30-min variability generated by WRF model. Finally, we comp compare the WRF model with the MAR (v3.3.) regional model using the same forcing at its lateral boundaries. This last one seems to suggest that the MAR model better simulates wind speeds at 10m and at 100m than WRF model and then that wind speed underestimation by WRF is well linked to the WRF physics itself.

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See detailÉtude des changements de circulation au-dessus de l'océan Austral en été
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

in Camberlin, Pierre; Richard, Yves (Eds.) Actes du XXVIIème colloque de l'Association de Climatologie - Climat : système & interactions (2014, June)

Over the five last decades, the reanalyses (ERA and NCEP/NCAR) show a strengthening of the pressure gradient between the southern hemisphere subtropical anticyclone belt and the southern circumpolar lows during summer. With the help of an automatic circulation type classification, we show that the strengthening of the pressure gradient is generalised to all circulation types and, paradoxically, it does not cause circulation changes. It is probably implied by the strengthening of the temperature gradient between the tropics and the South Pole, without consequences on the general circulation. Our classification also allows a successful comparison between the two reanalyses in a region where the observation data are rare.

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See detailÉvolutions multiples et intérêts nouveaux en matière de climatologie depuis 1970.
Erpicum, Michel

Scientific conference (2014, February 25)

Evolution of the knowledge of the main variables of the climates of the Earth according to the recent evolution of the principal tools of climatology and instrumental data coming from international or national networks or from experimental measurements conducted in Climatological or Meteorological Institutes.

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See detailDo global warming-induced circulation pattern changes affect temperature and precipitation over Europe during summer?
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

in International Journal of Climatology (2014)

Future climate change projections are not limited to a simple warming, but changes in precipitation and sea level pressure (SLP) are also projected. The SLP changes and the associated atmospheric circulation changes could directly mitigate or enhance potential projected changes in temperature and precipitation associated with rising temperatures. With the aim of analysing the projected circulation changes and their possible impacts on temperature and precipitation over Europe in summer [June–July–August (JJA)], we apply an automatic circulation type classification method, based on daily SLP, on general circulation model (GCM) outputs from the Coupled Model Intercomparison Project phase 5 (CMIP5) database over the historical period (1951–2005) and for climate under two future scenarios (2006–2100). We focus on summer as it is the season when changes in temperature and precipitation have the highest impact on human health and agriculture. Over the historical observed reference period (1960–1999), our results show that most of the GCMs have significant biases over Europe when compared to reanalysis data sets, both for simulating the observed circulation types and their frequencies, as well as for reproducing the intraclass means of the studied variables. The future projections suggest a decrease of circulation types favouring a low centred over the British Isles for the benefit of more anticyclonic conditions. These circulation changes mitigate the projected precipitation increase over north-western Europe in summer, but they do not significantly affect the projected temperature increase and the precipitation decrease over the Mediterranean region and eastern Europe. However, the circulation changes and the associated precipitation changes are tarnished by a high uncertainty among the GCM projections.

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See detailModelling of the present and future climate and surface mass balance of Svalbard with the regional climate model MAR
Lang, Charlotte; Fettweis, Xavier; Erpicum, Michel

Poster (2013, November 01)

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See detailAnalyse du « Dossier méthodologique relatif à l'élaboration d'une carte positive de référence traduisant le cadre actualisé, associée à un productible minimal par lot permettant de développer le grand éolien à concurrence d'un objectif de 3.800 GWh à l'horizon 2020 »
Canters, Frank; Cornet, Yves; De Keersmaecker, Marie-Laurence; De Maeyer, Philippe; Donnay, Jean-Paul; Erpicum, Michel; Fettweis, Xavier; Houbrechts, Geoffrey; Marion, Jean-Marc; Poty, Edouard; Thomas, Isabelle

Report (2013)

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See detailModelling of the surface mass balance of Svalbard with the regional climate model MAR
Lang, Charlotte; Fettweis, Xavier; Erpicum, Michel

Poster (2013, April 11)

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See detailEstimation of the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional climate model MAR
Fettweis, Xavier; Gallée, H.; van den Broeke, M.; Tedesco, M.; van Angelen, J.; Lenearts, J.; Erpicum, Michel

Conference (2013, April 10)

With the aim of estimating the sea level rise (SLR) coming from Surface Mass Balance (SMB) changes over the Greenland ice sheet (GrIS), we report future projections obtained with the regional climate model MAR, forced by outputs of three CMIP5 General Circulation Models (GCMs). Our results indicate that in warmer climates, the mass gained due to increased winter snowfall over GrIS does not compensate the mass lost through increased meltwater run-off in summer. All the MAR projections shows similar non-linear melt increases with rising temperatures as a result of the positive surface albedo feedback, because no change is projected in the general atmospheric circulation over Greenland. Nevertheless, MAR exhibits a large range in its future projections. By coarsely estimating the GrIS SMB changes from CMIP5 GCMs outputs, we show that the uncertainty coming from the GCM-based forcing represents about half of projected SMB changes. In 2100, the CMIP5 ensemble mean projects a SLR, resulting from a GrIS SMB decrease, estimated to be 4 2 cm and 9 4 cm for the RCP 4.5 and RCP 8.5 scenarios, respectively. However, these future projections do not consider the positive melt-elevation feedback. Sensitivity MAR experiments using perturbed ice sheet topographies consistent with the projected SMB changes highlight the importance of coupling climate models to an ice sheet model. Such a coupling will allow to consider the future response of both surface processes and ice-dynamic changes, and their mutual feedbacks to rising temperatures.

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See detailModeling of the present surface mass balance over the Ellesmere Island using the regional climate model MAR
Watelet, Sylvain; Noel, Brice; Fettweis, Xavier; Erpicum, Michel

Conference (2013, April)

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See detailHow does the ocean surrounding the Greenland ice sheet impact its surface mass balance ?
Noel, Brice; Watelet, Sylvain; Fettweis, Xavier; Erpicum, Michel

Poster (2013, April)

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See detailLatest results in forecasting and DLR related to Twenties and other projects
Nguyen, Huu-Minh; Doutreloup, Sébastien; Erpicum, Michel; Lilien, Jean-Louis

Conference (2013, March 05)

The goal of the meeting was to further (see Minutes of the WG3-DLR meeting which took place in Liège, Belgium, November 27th-28th 2012) investigate the “Dynamic Line Rating DLR” potential for the efficient management of electric grids in view of the increasing share of intermittent renewable energies (wind & solar) and to proceed with the preparation of two posi-tion papers dedicated to 1) DLR forecasting and 2) DLR planning. It was also aimed at finaliz-ing the Terms of Reference for the establishment of a new Working Group within the Cigré B2 Study Committee.

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See detailImportant role of the mid-tropospheric atmospheric circulation in the recent surface melt increase over the Greenland ice sheet
Fettweis, Xavier; Hanna, Edward; Lang, Charlotte; Belleflamme, Alexandre; Erpicum, Michel; Gallée, Hubert

in Cryosphere (2013), 7

Since 2007, there has been a series of surface melt records over the Greenland ice sheet (GrIS), continuing the trend towards increased melt observed since the end of the 1990's. The last two decades are characterized by an increase of negative phases of the North Atlantic Oscillation (NAO) favouring warmer and drier summers than normal over GrIS. In this context, we use a circulation type classification based on daily 500 hPa geopotential height to evaluate the role of atmospheric dynamics in this surface melt acceleration for the last two decades. Due to the lack of direct observations, the interannual melt variability is gauged here by the summer (June–July–August) mean temperature from reanalyses at 700 hPa over Greenland; analogous atmospheric circulations in the past show that ~70% of the 1993–2012 warming at 700 hPa over Greenland has been driven by changes in the atmospheric flow frequencies. Indeed, the occurrence of anticyclones centred over the GrIS at the surface and at 500 hPa has doubled since the end of 1990's, which induces more frequent southerly warm air advection along the western Greenland coast and over the neighbouring Canadian Arctic Archipelago (CAA). These changes in the NAO modes explain also why no significant warming has been observed these last summers over Svalbard, where northerly atmospheric flows are twice as frequent as before. Therefore, the recent warmer summers over GrIS and CAA cannot be considered as a long-term climate warming but are more a consequence of NAO variability affecting atmospheric heat transport. Although no global model from the CMIP5 database projects subsequent significant changes in NAO through this century, we cannot exclude the possibility that the observed NAO changes are due to global warming.

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See detailFuture projections of the Greenland ice sheet energy balance driving the surface melt
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

in Cryosphere (2013), 7

In this study, simulations at 25 km resolution are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios from three CMIP5 global circulation models (GCMs), in order to investigate the projected changes of the surface energy balance (SEB) components driving the surface melt. Analysis of 2000–2100 melt anomalies compared to melt results over 1980–1999 reveals an exponential relationship of the GrIS surface melt rate simulated by MAR to the near-surface air temperature (TAS) anomalies, mainly due to the surface albedo positive feedback associated with the extension of bare ice areas in summer. On the GrIS margins, the future melt anomalies are preferentially driven by stronger sensible heat fluxes, induced by enhanced warm air advection over the ice sheet. Over the central dry snow zone, the surface albedo positive feedback induced by the increase in summer melt exceeds the negative feedback of heavier snowfall for TAS anomalies higher than 4 °C. In addition to the incoming longwave flux increase associated with the atmosphere warming, GCM-forced MAR simulations project an increase of the cloud cover decreasing the ratio of the incoming shortwave versus longwave radiation and dampening the albedo feedback. However, it should be noted that this trend in the cloud cover is contrary to that simulated by ERA-Interim–forced MAR for recent climate conditions, where the observed melt increase since the 1990s seems mainly to be a consequence of more anticyclonic atmospheric conditions. Finally, no significant change is projected in the length of the melt season, which highlights the importance of solar radiation absorbed by the ice sheet surface in the melt SEB.

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See detailCurrent and future atmospheric circulation at 500 hPa over Greenland simulated by the CMIP3 and CMIP5 global models
Belleflamme, Alexandre; Fettweis, Xavier; Lang, Charlotte; Erpicum, Michel

in Climate Dynamics (2013), 41(7-8),

The Greenland ice sheet is projected to be strongly affected by global warming. These projections are either issued from downscaling methods (such as Regional Climate Models) or they come directly from General Circulation Models (GCMs). In this context, it is necessary to evaluate the accuracy of the daily atmospheric circulation simulated by the GCMs, since it is used as forcing for downscaling methods. Thus, we use an automatic circulation type classification based on two indices (Euclidean distance and Spearman rank correlation using the daily 500 hPa geopotential height) to evaluate the ability of the GCMs from both CMIP3 and CMIP5 databases to simulate the main circulation types over Greenland during summer. For each circulation type, the GCMs are compared to three reanalysis datasets on the basis of their frequency and persistence differences. For the current climate (1961–1990), we show that most of the GCMs do not reproduce the expected frequency and the persistence of the circulation types and that they simulate poorly the observed daily variability of the general circulation. Only a few GCMs can be used as reliable forcings for downscaling methods over Greenland. Finally, when applying the same approach to the future projections of the GCMs, no significant change in the atmospheric circulation over Greenland is detected, besides a generalised increase of the geopotential height due to a uniform warming of the atmosphere.

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See detailRainfall retrieval using Spinning Enhanced Visible and Infrared Imager (SEVIRI-MSG) and Cloud Physical Properties (CPP) algorithm : validation over Belgium and applications
Beaumet, Julien; Clerbaux, Nicolas; Fettweis, Xavier; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (2013), 61(2013-2), 5-14

Precipitation is the main variable of the water cycle and the water resources availability. Despite numerous available methods, precipitation measurements are still insufficient to quantify with certainty ongoing changes and to provide data for numerical models validation. Roebeling & Holleman (2009) presented the Cloud Physical Properties algorithm using data from the SEVIRI instrument on board Meteosat Second Generation. The goal of present study is to extend previous validations and verify the algorithm performances throughout yearly and daily cycles in order to identify possible use and applications. A seven-years data set of parallax-shift corrected clouds and precipitation data over Western Europe have therefore been processed using CPP algorithm. Results are encouraging for both precipitation areas delimitation and rain rates assessment. However, rain rates estimation are strongly affected by sun zenith angle with increasing overestimation for sza above 60°. Systematic errors also affect the retrieval of cloud properties for very thick clouds with an overestimation of extreme precipitation events.

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See detailCurrent net ecosystem exchange of CO2 in a young mixed forest: any heritage from the previous ecosystem?
Violette, Aurélie; Heinesch, Bernard; Erpicum, Michel; Carnol, Monique; Aubinet, Marc; François, Louis

Poster (2013)

For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for prediction of the evolution of carbon cycle and climate, major uncertainties remain on the ecosystem respiration (Reco, which includes the respiration of above ground part of trees, roots respiration and mineralization of the soil organic matter), the gross primary productivity (GPP) and their difference, the net ecosystem exchange (NEE) of forests. These uncertainties are consequences of spatial and inter-annual variability, driven by previous and current climatic conditions, as well as by the particular history of the site (management, diseases, etc.). In this study we focus on the carbon cycle in two mixed forests in the Belgian Ardennes. The first site, Vielsalm, is a mature stand mostly composed of beeches (Fagus sylvatica) and douglas fir (Pseudotsuga menziesii) from 80 to 100 years old. The second site, La Robinette, was covered before 1995 with spruces. After an important windfall and a clear cutting, the site was replanted, between 1995 and 2000, with spruces (Piceas abies) and deciduous species (mostly Betula pendula, Aulnus glutinosa and Salix aurita). The challenge here is to highlight how initial conditions can influence the current behavior of the carbon cycle in a growing stand compared to a mature one, where initial conditions are supposed to be forgotten. A modeling approach suits particularly well for sensitivity tests and estimation of the temporal lag between an event and the ecosystem response. We use the forest ecosystem model ASPECTS (Rasse et al., Ecological Modelling 141, 35-52, 2001). This model predicts long-term forest growth by calculating, over time, hourly NEE. It was developed and already validated on the Vielsalm forest. Modelling results are confronted to eddy-covariance data on both sites from 2006 to 2011. The main difference between both sites seems to rely on soil respiration, which is probably partly a heritage of the previous ecosystem at the young forest site.

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See detailOn the possibility to develop a rainfall data set over Belgium and Europe for climate monitoring using SEVIRI data : Validation and application of Cloud Physical Properties algorithm from the KNMI
Beaumet, Julien; Erpicum, Michel; Fettweis, Xavier; Clerbaux, Nicolas

Conference (2012, September 13)

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See detailFuture projections of the Greenland ice sheet surface mass balance simulated by the regional climate model MAR forced by three CMIP5 global models.
Fettweis, Xavier; Franco, Bruno; Lang, Charlotte; Erpicum, Michel

Conference (2012, September 11)

As part of the ICE2SEA project, the regional climate model MAR was forced by the global models HadCM3 and ECHAM5 for making future projections of the Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB) over 1980-2099 at a resolution of 25km. However, the comparison with MAR forced by the ERA-40 reanalysis over 1980-1999 shows that MAR forced by these GCMs is not able to represent reliably the current SMB due to biases in the general circulation and in the free atmosphere summer temperature modelled by these GCMs around the GrIS. That is why, we present here first results of MAR forced by the next generation of GCMs from the CMIP5 data base (CanESM2, NorESM1 and MIROC5 here). The comparison with the ERA-INTERIM forced MAR simulations over current climate is a lot of better, which increases the reliability and the interest of these new MAR projections. In addition, the new scenarios (RCP 2.6, 4.5, 6.0 and 8.5) of the next IPCC Assessment Report (AR5) are used here. These new simulations show notably that the response of SMB to rising temperature is not a linear function of the temperature anomalies due to the positive albedo feedback which enhances the surface melt. For 2100, in case of extreme rising temperature (RCP 8.5 scenario), MAR simulates a surface GrIS mass loss corresponding to a cumulated sea level rise (SLR) of about 15 cm since 2000! Mainly the changes in SMB and in surface energy balance will be discussed here and estimations of the GrIS surface melt contribution to the SLR using all the CMIP5 outputs will be given.

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See detailRECOURS À UNE CAMPAGNE DE MESURES TOPOCLIMATIQUES APPLIQUÉE POUR UNE ÉTUDE COMPARATIVE DE VARIABLES MÉTÉOROLOGIQUES CONCOMITANTES PROVENANT DES STATIONS MÉTÉOROLOGIQUES DE BRUGGE ET DU MONT RIGI EN BELGIQUE
Pirard, Xavier; Jorion, Nicolas; Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

Poster (2012, September 07)

Une station météorologique automatique munie d’un mât de 10 mètres a été installée à l’Ouest de l’agglomération urbaine de Brugge (Belgique) par le Laboratoire de Climatologie et Topoclimatologie de l’ULg. Elle a été équipée afin de confirmer la bonne qualité des prévisions météorologiques du modèle WRF établies dans le cadre du projet européen TWENTIES. Les données récoltées de minute en minute par cette station météorologique offrent également l’opportunité de mettre en évidence le détail de situations météorologiques bien particulières comme celles correspondant aux passages de fronts.

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See detailEvaluation des modèles climatiques régionaux MAR et WRF sur le Svalbard
Lang, Charlotte; Fettweis, Xavier; Erpicum, Michel

Poster (2012, September)

: Il est bien connu que les zones de hautes latitudes sont très sensibles aux changements climatiques. A cause du réchauffement global, la fonte des calottes a augmenté, ce qui à son tour a une influence sur le climat via des modifications de la circulation thermohaline, la rétroaction de l’albédo de la glace, l’augmentation du niveau des mers… Nous avons comparé le climat du Svalbard modélisé par deux modèles régionaux (MAR et WRF) à une résolution de 10 km sur la période 2000-2010 à des mesures provenant de plusieurs stations météorologiques localisées dans différentes régions de l’archipel afin d'évaluer lequel de ces modèles pouvait représenter au mieux le climat du Svalbard.

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See detailLes modèles globaux projettent-ils plus de blocages anticycloniques en Europe pour le futur ?
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

in Bigot, Sylvain; Rome, Sandra (Eds.) XXVème colloque de l'Association Internationale de Climatologie - Les climats régionaux : observation et modélisation (2012, September)

The IPCC projects more frequent and longer heat waves and droughts during summer for future over Western Europe. These extreme events occur during anticyclonic blocking events. We use atmospheric circulation type classifications to determine if the models project an increase of the number and the persistence of these anticyclonic blockings. For recent climate, the number of blocking events depends on the ability of the models to reproduce the observed general circulation. The future projections do not show any systematic evolution of the number of anticyclonic blockings over Western Europe. Nevertheless, other changes like an increase of the temperature will lead to more frequent heat waves and droughts.

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See detailÉVOLUTION DU COMPORTEMENT DU VENT ET DE SON POTENTIEL POUR LA PRODUCTION D'ÉNERGIE ÉOLIENNE DURANT LES 30 DERNIÈRES ANNÉES : LE CAS DE LA BELGIQUE
Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

in Bigot, Sylvain; Rome, Sandra (Eds.) Les climats régionaux : observation et modélisation. (Actes du colloque organisé à Grenoble du mercredi 5 au samedi 8 septembre 2012) (2012, September)

Chaque année, le nombre d'éoliennes dans le monde augmente de façon significative suite notamment aux politiques encourageant les productions d'énergie verte afin d’atténuer le réchauffement climatique. Toutefois, ce type d'énergie est tributaire de la météo. Cela implique que la production d'énergie éolienne est irrégulière à courte échelle de temps. Cependant, la disponibilité d’électricité de courtes périodes de temps est très importante à connaitre pour les producteurs d'énergie ainsi que pour les gestionnaires de réseaux. Pour ces raisons, il nous parait primordial d’analyser l’évolution de l’intermittence de la vitesse du vent sur les 30 dernières années (1979-2009). Pour ce faire nous utilisons le modèle WRF forcé par les réanalyses ERA-Interim, les réanalyses NCEP2 et certains modèles du GIEC (base de données CMIP5).

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See detailPower line dynamic rating: forecasting potential period of low wind speed is crucial
Nguyen, Huu-Minh; Doutreloup, Sébastien; Erpicum, Michel; Schell, Peter

Conference (2012, September)

The replacement and building of new electrical power lines (50 000 km in Europe) can’t cope with the growth of RES development in EU for the ten upcoming years. New solutions have to be found to manage such power transmission needs. Dynamic Line Rating (DLR) systems are part of the global solution. They allow to increase the power line capacity by an average 20% over the static rating (which is defined as the maximum current-carrying capacity as designed). The ampacity or thermal rating, is calculated thanks to (i) sensors installed directly on the power line conductors, like Ampacimon, (ii) weather data, and (iii) standard thermal models (IEEE, CIGRE). However, in order to be fully effective and to allow an efficient use of assets, ampacity calculation in real-time is not enough; it has to be forecasted as well. Beyond 6h-forecast, weather forecasts are necessary to compute the line ampacity up to two days ahead, as needed by network operation. As wind convection has a major impact on conductor cooling, even low wind speeds (2m/s up to 5m/s) allow a huge ampacity increase (the actual rating can be doubled). Therefore, low wind speed forecast up to 2-days ahead finds a major application in dynamic rating of overhead transmission and distribution lines.

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See detailImpact of spatial resolution on the modelling of the Greenland ice sheet surface mass balance between 1990–2010, using the regional climate model MAR
Franco, Bruno; Fettweis, Xavier; Lang, Charlotte; Erpicum, Michel

in Cryosphere (2012), 6

With the aim to force an ice dynamical model, the Greenland ice sheet (GrIS) surface mass balance (SMB) was modelled at different spatial resolutions (15-50 km) for the period 1990-2010, using the regional climate model MAR (Modèle Atmosphérique Régional) forced by the ERA-INTERIM reanalysis. This comparison revealed that (i) the inter-annual variability of the SMB components is consistent within the different spatial resolutions investigated, (ii) the MAR model simulates heavier precipitation on average over the GrIS with diminishing spatial resolution, and (iii) the SMB components (except precipitation) can be derived from a simulation at lower resolution with an intelligent interpolation. This interpolation can also be used to approximate the SMB components over another topography/ice sheet mask of the GrIS. These results are important for the forcing of an ice dynamical model, needed to enable future projections of the GrIS contribution to sea level rise over the coming centuries.

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See detailEvaluation of the MAR and WRF regional climate models over Svalbard
Lang, Charlotte; Fettweis, Xavier; Doutreloup, Sébastien; Erpicum, Michel

Conference (2012, June 01)

It is well known that high latitude zones are very sensitive to climate change. As a result of global warming, ice sheet melting has increased which in turn has an influence on climate through modifications of the thermohaline circulation, feedback of ice albedo, sea level rise... Svalbard is an archipelago between 74 and 81°lat N and 60 percent of its area (62 248 km2) is covered with glaciers and ice sheets. The impact of global warming on the Svalbard cryosphere can be estimated with climate models. However, we need to use regional climate models as they offer the possibility of a higher resolution than general circulation models. We have ran two regional climate models (MAR and WRF) at a 10-kilometre resolution between 2006 and 2010 over Svalbard and compared their simulated climate to near surface measurements at several weather stations through the archipelago in order to determine which one of them could best represent the Svalbard climate.

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See detailAre the CMIP5 GCMs able to simulate atmospheric blocking situations over Europe ?
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

Poster (2012, April 26)

Some studies show that most General Circulation Models (GCMs) have difficulties to simulate the main observed circulation patterns and their frequencies. However, this does not only impact the GCM based projections for future climate, but also the results of downscaling methods using the circulation simulated by GCMs as forcing. Indeed, the downscaling methods are not able to correct the biases introduced by the GCM simulations in the free atmosphere. Here, we focus on the anticyclonic blocking situations over western Europe for summer (June, July and August). Indeed, these blocking situations, which are often related to droughts and heat waves, could become more frequent due to global warming. Moreover, their frequency and persistence depend on the variability of the circulation, which is known to be difficult to reproduce by the GCMs. In order to evaluate the ability of the GCMs to reproduce the observed frequency and persistence of blocking situations, we compare them with two reanalysis datasets (NCEP-NCAR 1 and ECMWF ERA-40) by using an automatic circulation type classification. The daily geopotential height at 500 hPa over the last 30 years of the current climate simulation (Historical experiment, 1976-2005) of all available CMIP5 GCMs prepared for the upcoming IPCC report AR5 is used here. The circulation type classification groups similar daily circulation situations together on basis of a leader-algorithm to obtain a few homogeneous circulation types describing the general circulation of the region. Thus, the frequency and the persistence of each circulation type can be analysed on a daily timescale. We show that the ability of the GCMs to reproduce the observed frequency and persistence of blocking situations is influenced by the anomalies in their circulation type frequency repartition. So, the GCMs which underestimate the frequency of the anticyclonic types tend to simulate less and shorter blocking situations. The contrary is observed for GCMs that overestimate the frequency of these circulation types. This rises questions about the reliability of the future projections for events related to blocking situations. Indeed, when applying the same approach as for the current climate to the future projections (experiments RCP4.5 and RCP8.5), it seems that the blocking situations become more frequent and persistent. However, when considering only the circulation patterns by removing the mean geopotential height increase due to global warming, there is no significant circulation change till 2100. This means that the GCMs conserve their circulation biases in spite of climate change and so, the frequency and the persistence of the blocking situations are projected to remain almost the same as those simulated for the current climate.

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See detailEvaluation of the regional climate model WRF over Svalbard
Lang, Charlotte; Fettweis, Xavier; Doutreloup, Sébastien; Erpicum, Michel

Poster (2012, April 24)

It is well known that high latitude zones are very sensitive to climate change. As a result of global warming, ice sheet melting has increased which in turn has an influence on climate through modifications of the thermohaline circulation, feedback of ice albedo, sea level rise, … Svalbard is an archipelago between 74 and 81°lat N and 60 percent of its area (62 248 km2) is covered with glaciers and ice sheets. The impact of global warming on the Svalbard cryosphere can be estimated with climate models. However, we need to use regional climate models as they offer the possibility of a higher resolution than general circulation models. We have ran two regional climate models (MAR and WRF) at a 10-kilometre resolution between 2006 and 2010 over Svalbard and compared their simulated climate to near surface measurements at several weather stations through the archipelago in order to determine which one of them could best represent the Svalbard climate.

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See detailEstimation, prévision et contrôle du gisement solaire en région wallonne
Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

Poster (2012, April 23)

Présentation des activités et des recherches du Laboratoire de Climatologie et Topoclimatologie de l'Université de Liège dans le domaine du rayonnement solaire

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See detailApport de la disdrométrie laser au service de la climatologie des hydrométéores
Erpicum, Michel; Fettweis, Xavier; Jorion, Nicolas; Pirard, Xavier; Sougnez, Arnaud

in Carrega, Pierre (Ed.) Actes des journées de climatologie du CNFG : Climat et Société, Thème : climat et eau, Lyon 2011 (2012, March)

analysis of several rainy days with the support of laser disdrometers in temperate climate (Belgium)

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See detailÉtude fréquentielle de données via la transformée en ondelette : application aux cycles climatiques
Mabille, Georges; Fettweis, Xavier; Erpicum, Michel; Nicolay, Samuel

in Bulletin de la Société Géographique de Liège (2012), 58

Understanding the climate requires a complex study of time series connected to weather parameters. The climatologist frequently applies signal processing tools and often uses the harmonic analysis and the Fourier transform. This article is dedicated to the description of a new tool, elaborated by mathematicians, which completes the outfit of intruments intended for signal analysis. The scale spectrum, which synthetizes a part of the information supplied by the wavelet transform, possesses the property to reveal pseudo-cycles which evolves around an average period. When applied to air surface temperature time series obtained from more than one hundred weather stations, to reanalysis data and to climatic indices which characterize the tropospheric flows, the wavelet transforms and the scale spectra reveal cycles with periods close to 30 months and 42 months. The Solar parameters analysis also leads to the existence of pseudo-cycles with frequencies corresponding to those found in the temperature time series and climatic indices.

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See detailEvolution of wind behaviour and of its potential for wind power production in Belgium during the last 22 years : a comparison between WRF forced by NCEP2 reanalysis and WRF forced by ERA-INTERIM reanalysis
Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

Conference (2011, September 16)

The number of wind turbines in the world grows significantly every year due to politics proposing green energy productions as solutions to mitigate climate change effects. However, this kind of energy is dependent on the weather. This implies that the wind production is irregular at a very short time scale. But the short time scale availability of the wind-based energy is important to the producers of energy as well as to the electric grid managers because the wind energy production can rise or fall rapidly which creates some financial and voltage variations. For these reasons, we study the past evolution of the availability of the wind quantity by analysing the intermittence of the wind speed in Belgium during the last 22 years (1989-2010). To reach this goal, we use the regional model WRF (Weather and Research Forecast model) developed by the UCAR community users. In a first time, the WRF model is forced by the NCEP2 reanalysis outputs to obtain a regionalisation of the weather conditions over a domain centred on Belgium at a resolution of 10 km. This resolution allows to capture the minute-based time scale variability of wind speed and consequently the irregular behaviour of the wind power production. In a second time, the WRF model is forced by the ERA-Interim reanalysis outputs with the same configuration. To obtain a value of the wind intermittence, we calculate the persistence of a wind blowing continuously with a minimum speed of 1 ms-1, then the persistence of a wind blowing continuously with a minimum speed of 2 ms-1, etc. The persistence of the wind speed and its evolution over 22 years are characterised by : (a) the mean wind speed over a fixed period (monthly, seasonally, … ), (b) the mean duration of a wind speed above x ms-1 over the same fixed period and (c) the evolution of (a) and (b) during the studied period. This analysis is made with the outputs of WRF-NCEP2 and with the outputs of WRF-Interim allowing to evaluate the impact of forcing fields into WRF-based wind climatology.

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See detailInfluence de la résolution spatiale sur la modélisation du bilan de masse en surface de la calotte glaciaire du Groenland
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

in Fazzini, Massimiliano; Beltrando, Gérard (Eds.) Actes du XXIVe colloque annuel de l’Association Internationale de Climatologie : Climat Montagnard et Risques (2011, September 07)

By using the regional climate model MAR (Modèle Atmosphérique Régional), we have modelled the Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB) at 20, 25, 30, 40 and 50km resolution to assess the impact of the spatial resolution. As part of the ICE2SEA project, the 25km-resolution SMB outputs of the MAR model are used as forcing fields for ice sheet models, in order to produce projections of the GrIS contribution to sea-level rise over the next 200 years. However, the ice sheet models often run at a higher resolution (typically 5-10km) than the current MAR resolution (25km). Such higher-resolution runs of the MAR model on the same integration domain generate a significant additional computing time and are not doable until now. That is why several enhanced SMB interpolations are tested here in order to reduce biases when interpolating the MAR outputs onto higher resolution, in the framework of the ICE2SEA project.

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See detailInfluences de l'environnement d'un parc éolien sur la prévision de sa production électrique à l'aide des modèles GFS (50km/3h) et WRF (2km/15min) : Le cas du parc éolien d'Amel (Haute-Belgique)
Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

in Fazzini, Massimiliano; Beltrando, Gérard (Eds.) Actes du XXIVème Colloque International AIC : Climat Montagnard et Risques (2011, September 06)

The economic and climate contexts require to use more electricity from wind farms. However this kind of production is intermittent, therefore it is necessary to forecast this resource at least 1 day ahead. Our laboratory has developed a forecasting model of wind-based electricity generation based on a global meteorological model (GFS) with a resolution of 50 km and 3 h. But this model has a resolution too coarse for a wind farm. So we have configured the regional model WRF with resolution of 2 km and 15 min to obtain better forecasts. Finally, the WRF model provides better forecasts, but both must be adjusted to take into account the direct environment of the wind farm.

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See detailCirculation atmosphérique simulée par les modèles de circulation générale en Europe de l'ouest : évaluation et projections futures
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

in Fazzini, Massimiliano; Beltrando, Gérard (Eds.) XXIVème colloque de l'Association Internationale de Climatologie - Climat montagnard et risques (2011, September)

Atmospheric circulation simulations from general circulation models are used as forcing for downscaling methods and for future projections. Thus, it is essential to evaluate them. An automatic circulation type classification is applied to daily 500 hPa geopotential height data. Firstly, the classification is done for the NCEP-NCAR 1 reanalysis, and then the main circulation types are imposed to the simulations of six general circulation models. For recent climate (20C3M scenario), it appears that most models are not able to simulate well the circulation over western Europe, due to biases in the mean geopotential height and an underestimation of the circulation variability. For future climate (A1B scenario), a general increase of the geopotential height is projected, leading to the emergence of new circulation types.

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See detailEstimation of the Sea Level Rise by 2100 Resulting from Changes in the Surface Mass Balance of the Greenland Ice Sheet
Fettweis, Xavier; Belleflamme, Alexandre; Erpicum, Michel; Franco, Bruno; Nicolay, Samuel

in Blanco, Juan; Kheradmand, Houshang (Eds.) Climate Change - Geophysical Foundations and Ecological Effects (2011)

We present here future projections of the Greenland climate performed by the regional climate model MAR coupled with a snow model and forced by two scenarios of greenhouse gas emissions from the global model CanESM2 of the next IPCC assessment report (AR5). Knowing that MAR forced by CanESM2 over the current climate (1970-1999) compares well with the reference MAR simulation performed by using the ERA-40 reanalysis as forcing, this gives us confidence in our future projections. For the RCP4.5 scenario (optimistic) and respectively RCP8.5 scenario (pessimistic), MAR projects a sea level rise in 2100 of 6.5 +/- 1.5 cm and respectively 14+/-2 cm as result of increasing surface melt of the Greenland ice sheet over 2000-2100. It is true that MAR projects a small increase of snowfall in the winter because the atmosphere will be warmer and therefore can contain more water vapor. But this is not sufficient to offset the acceleration of melt, notably for the scenario RCP8.5 which projects an increase of 10 °C in 2100 above the ice sheet. This work fits in the ICE2SEA project (http://www.ice2sea.eu) of the 7th Framework Program (FP7) which aims to improve the projections of the continental ice melting contribution to sea level rise.

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See detailAnalysis of the past (1970-1999) and future (2046-2065 and 2081-2100) evolutions of precipitation and temperature, in the Province of Binh Thuan, South East Vietnam, based on IPCC models
Doutreloup, Sébastien; Erpicum, Michel; Fettweis, Xavier; Ozer, Pierre

in Proceedings of the 1st International Conference on Energy, Environment and Climate Change (2011, August)

Natural resource-dependent societies in developing countries are facing increased pressures linked to global climate change. The Province of Binh Thuan, in South East Vietnam, where rainfall is on average 500 to 700 mm but can drop as low as 350 mm in some years, knows a recent increase of agricultural activities in order to contribute to reduce poverty although the technical efficiency of Binh Thuan is still very low. Within this framework of higher dependency of the local economy on the agricultural sector, there is growing evidence that changes in climate extremes are increasing exposure of currently vulnerable rural populations. In order to assess the future climate of the province of Binh Thuan, only three models able to simulate the current climate in the study area were used out of the 24 selected by the IPCC: CCCMA-T47, INGV and IPSL. The future climate projections (that is 2046-2065 and 2081-2100 compared to historical data 1970-1999) were focused on two targets: [i] assessing changes in climate statistics, and [ii] analysing the beginning and the end of the rainy season. [i] The first analysis indicates an increase of mean temperature of about 1.6°C (over 2046-2065) and 2.5°C (over 2081-2100) and an increase of extreme temperatures and extreme rainfall events. However, no significant changes about the evolution of the annual amount of precipitation were found. [ii] The second analysis indicates that the dry season is likely to be longer in 2046-2065 owing to a delay in the onset of the rainy season (up to 15 days) accompanied by an earlier end of the rainy season (up to 30 days). Although it must be kept in mind that precipitations are the most difficult climate variable to predict, it is likely that increasing water needs to support expending agriculture within the context of climate change in the Province of Binh Thuan will be a challenge. Indeed, extreme rainfall events are likely to increase and unchanged yearly amounts of precipitation should be concentrated in time.

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See detailLes empreintes thermiques routières - Convention 2010-2011
Erpicum, Michel; Frédéric, Marc; Jorion, Nicolas; Pirard, Xavier

Report (2011)

Présentation des résultats des empreintes thermiques routières. La convention hiver 2010-2011 couvre 8 districts de la Région wallonne dans la province du Luxembourg.

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See detailEvaluation of the present and future general circulation over western Europe simulated by the IPCC AR5/CMIP5 GCMs with the help of a circulation type classification
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

Conference (2011, April 08)

Downscaling methods forced by General Circulation Model (GCM) simulations are not able to correct the biases in the general circulation simulated by the GCMs. Moreover, since the GCMs have a coarse spatial resolution, they have difficulties to simulate reliably ground variables like temperature and precipitation which are affected by topography, land use and local features. So, we can attempt that they simulate better the large-scale atmospheric circulation. That is why it is of special interest to evaluate the GCM simulations of atmospheric circulation for current climate by comparing them with the NCEP-NCAR 1 and the ECMWF reanalysis data over 1961-1990. This analysis is done over western Europe for summer (JJA) and winter (DJF) for the GCMs (available on http://cmippcmdi.llnl.gov/cmip5/) proposed by the IPCC for its upcoming report (AR5). The method used is an automated circulation type classification based on the daily geopotential height at 500 hPa. It is a leader-algorithm correlation based method taking part of the COST733CAT classification catalogue. Unlike the usually used methods based on the monthly mean circulation, this approach allows a precise analysis of each circulation type. So, it gives much more information on the ability of the GCMs to simulate the different circulation types and consequently the climatic variability of a region. In order to allow a direct comparison between the GCM simulations and the reanalysis data, the classification is done first only for the reanalysis dataset over 1961-1990. Then, the main types individualised here are imposed for the classification of the GCM outputs. Since the circulation types are the same, the comparison between the datasets can be made on the basis of the differences of the frequency distribution throughout the classes. Moreover, the mean intraclass repartition of the circulation situations may differ from one dataset to another. So, the study of this mean and its standard deviation gives an idea of the differences between the reanalysis and the GCMs within each class. Firstly, this approach is applied to current climate (1961-1990) for evaluating the ability of the GCMs driven by the historical experiment to simulate the climate of the last decades over western Europe. In fact, if one GCM is not able to reproduce reliably the main characteristics of the current climate, its future projections may be questionable. Then, the best matching GCMs are retained and the same approach is applied to the future simulations driven by RCP concentrations or emissions (2011-2040, 2041-2070 and 2071-2100). So, the evolution of the frequency of the circulation types and maybe the appearance of new types can be analysed under climate change conditions. Moreover, it is interesting to compare the uncertainty of the current climate simulations to the projected changes for future climate. If the uncertainty is of the same order or higher than the projected changes, the reliability of the simulations for future climate may be very questionable.

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See detailExplanation of the extreme low surface mass balance over the Greenland ice sheet in 2010 with the help of a regional climate model and a circulation type classification.
Fettweis, Xavier; van den Broeke, Michiel; van de Berg, Willem Jan; Tedesco, Marco; Belleflamme, Alexandre; Franco, Bruno; Erpicum, Michel

Conference (2011, April 06)

The regional climate models MAR and RCMO show that the surface mass balance (SMB) rate of the whole Greenland ice sheet (GrIS) is the lowest in 2010 since 50 years. This record is a combination of an abnormal dry year and an exceptional melt in summer confirmed by ground measurements and satellite-derived observations. An automated circulation type classification (CTC) is used for detecting anomalies in the daily atmospheric circulation at 500hPa over the Greenland ice sheet during 2010. The CTC reveals that the low snow accumulation is due to the general circulation (negative NAO index) while the record melt in summer is rather a consequence of the well known surface albedo-temperature feedback induced by - a warmer and thinner than normal snowpack above the bare ice at the end of the spring. - an earlier beginning of the melt season. - a drier summer. - an exceptional persistence of atmospheric circulations inducing warm and dry conditions over the GrIS. All these anomalies induced in summer 2010 an exceptional time exposure of bare ice areas (with a lower albedo than snow) over the GrIS which impacts the surface melt. Sensitivity experiments carried out by the MAR model allow to estimate the importance of each anomaly in the record simulated melt of summer 2010.

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See detailEvaluation of the present and future general circulation over Greenland simulated by the IPCC AR5/CMIP5 GCMs with the help of a circulation type classification
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

Poster (2011, April 05)

Future projections of the Greenland ice sheet melt are based on General Circulation Model (GCM) simulations. In particular, the reliability of downscaling methods forced by these simulations depends on the quality of the atmospheric circulation simulated by GCMs. Therefore, it is essential to analyse and evaluate the GCMs modelled general circulation for current climate (1961-1990). Atmospheric circulation type classifications offer a very interesting approach for evaluating the GCM-based circulation at a daily time scale compared to the most used methods based only on monthly means. Indeed, the circulation type classification allows a precise and detailed analysis of each circulation type and so, it gives much more information on the ability of GCMs to simulate the different circulation types and consequently the climatic variability of a region. In fact, exceptional circulation events over Greenland, which cannot be taken into account by the monthly mean approach, have much more impact on the melt than the mean atmospheric state. Thus, an automated correlation-based atmospheric circulation type classification (CTC) is used for evaluating the new GCM outputs (available on http://cmip-pcmdi.llnl.gov/cmip5/) computed for the upcoming IPCC report (AR5). The daily geopotential height at 500 hPa simulations of the GCMs for current climate are compared to the NCEP-NCAR 1 and the ECMWF reanalysis data for the summer months (JJA), when melt is the most important. To achieve this, the classification is first done for the reanalysis data over 1961-1990 and afterwards, the types of the reanalysis based CTC are imposed for classifying the GCM datasets over 1961-1990 (from the historical experiment) to allow a direct type per type comparison based on the frequency distribution of each dataset. This approach also gives the opportunity to study the intraclass repartition differences between the reanalysis and the GCMs. After the evaluation of the GCM simulations for current climate, the future projections driven by RCP concentrations or emissions (2011-2040, 2041-2070 and 2071-2100) from the best matching GCMs are analysed in the same way. For current climate, it clearly appears that only a few GCMs are able to reproduce reliably the variability of the atmospheric circulation over Greenland during summer. The differences of frequency between the GCMs and the reanalysis are mainly due to biases of the geopotential height which is systematically over or underestimated by most GCMs and to the underestimation of the variability of the circulation by most GCMs. For future projections, no new circulation types are detected, but rather a general increase of the mean geopotential height regardless of the circulation type. It is also important to note that for many GCMs, the uncertainty of the current climate simulations (given by the differences of the classification results between the GCM simulations for current climate and the reanalysis data for the same time) are of the same order than the projected changes for future climate. Therefore, these projections may be questionable.

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See detailImpact of the spatial resolution on the Greenland Ice Sheet Surface Mass Balance modelling using the regional climate model MAR with the aim to force an ice sheet model.
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

Poster (2011, April 05)

By using the regional climate model MAR (Modèle Atmosphérique Régional), validated for Greenland at 25km resolution and forced every 6 hours with the ERA-INTERIM reanalysis (Fettweis 2007, Fettweis et al. 2010), we have modelled the Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB) at 20, 25, 30, 40 and 50km resolution to assess the impact of the spatial resolution. As part of the ICE2SEA project, the 25km-resolution SMB outputs of the MAR model are used as forcing fields for ice sheet models, in order to produce future projections of the GrIS contribution to sea-level rise over the next 200 years. Although the current spatial resolution of the MAR model (25km) is much higher than the general circulation models (GCM) resolution (150-300km), the ice sheet models often run at a higher resolution (typically 5-10km). Nevertheless, such higher-resolution runs of the MAR model on the same integration domain generate a significant additional computing time and are not doable until now. Moreover, conventional linear interpolations of the SMB outputs onto a higher-resolution grid, generally induce biases because ice sheet masks at different spatial resolutions do not match and the SMB is a very complex function of the spatial resolution and the topography . That is why several enhanced SMB interpolations are tested here in order to reduce biases when interpolating the MAR outputs onto higher resolution, in the framework of the ICE2SEA project.

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See detailEvaluation of the Greenland ice sheet surface mass balance simulated by a regional climate model forced by some selected IPCC AR5/CMIP5 AOGCMs over the current climate.
Fettweis, Xavier; van den Broeke, Michiel; van de Berg, Willem Jan; Belleflamme, Alexandre; Franco, Bruno; Erpicum, Michel

Conference (2011, April 05)

Abstract. As part of the ICE2SEA project, the regional climate model MAR was forced by the general circulation model ECHAM5 for making future projections of the Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB) over 1980-2099 at a resolution of 25km. For the A1B scenario, MAR projects a highly negative (-500 GT/yr) SMB rate at the end of this century and a induced mass loss corresponding to a sea level rise of ~7 cm over 2000-2100. However, the comparison with MAR forced by the ERA-40 reanalysis over 1980-1999 shows that MAR forced by the 20C3M scenario is not able to represent reliably the current SMB due to biases in the general circulation and in the free atmosphere summer temperature modeled by ECHAM5 around the GrIS. These biases induce in MAR an underestimation of the snow accumulation and an overestimation of the surface melt. Therefore, this questions the reliability of these ECHAM5-forced future projections, knowing that i) these biases could be amplified in future and that ii) the MAR outputs are used to force ice sheets models for the ICE2SEA project. That is why, by waiting the outputs from the next generation of GCMs (CMIP5), we investigate the impacts of current climate biases over the future projections and we suggest corrections of ECHAM5 forcing files for having a better agreement with the ERA-40 forced simulation. This is useful for the ice sheet model wanting to use the absolute values of MAR future projections instead of anomalies.

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See detailEvolution of wind behaviour and of its potential for wind power production in Belgium during the last 30 years.
Doutreloup, Sébastien; Fettweis, Xavier; Sacré, Bernard; Erpicum, Michel

Poster (2011, April 04)

The number of wind turbines in the world grows significantly every year due to politics proposing green energy productions as solutions to mitigate climate change effects. However, this kind of energy is dependent on the weather. This implies that the wind production is irregular at a very short time scale. But the short time scale availability of the wind-based energy is important to the producers of energy as well as to the electric grid managers because the wind energy production can rise or fall rapidly which creates some financial and voltage variations. For these reasons, we study the past evolution of the availability of the wind quantity by analysing the intermittence of the wind speed in Belgium during the last 30 years. To reach this goal, we use the regional model WRF (Weather and Research Forecast model) developed by the UCAR community users. The WRF model is forced by the NCEP2 Reanalysis model to obtain a regionalisation of the weather conditions over a domain centred on Belgium at a spatiotemporal resolution of 10 km and 1 min. This resolution allows to capture the minute-based time scale variability of wind speed and consequently the irregular behaviour of the wind power production. To obtain a value of the wind intermittence, we calculate the persistence of a wind blowing continuously with a minimum speed of 1 ms-1, then the persistence of a wind blowing continuously with a minimum speed of 2 ms-1, etc. The persistence of the wind speed and its evolution over 30 years are characterised by : (a) the mean wind speed over a fixed period (monthly, seasonally, … ), (b) the mean duration of a wind speed above x ms-1 over the same fixed period and (c) the evolution of (a) and (b) during the studied period. This study will show the evolution during the last decades of the wind behaviour in Belgium and its potential for electricity production.

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See detailImpact of the spatial resolution on the Greenland ice sheet surface mass balance modelling using the regional climate model MAR.
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

Conference (2011, January 14)

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See detailPresent and future climates of the Greenland ice sheet according to the IPCC AR4 models
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel; Nicolay, Samuel

in Climate Dynamics (2011), 36

The atmosphere–ocean general circulation models (AOGCMs) used for the IPCC 4th Assessment Report (IPCC AR4) are evaluated for the Greenland ice sheet (GrIS) current climate modelling. The most suited AOGCMs for Greenland climate simulation are then selected on the basis of comparison between the 1970–1999 outputs of the Climate of the twentieth Century experiment (20C3M) and reanalyses (ECMWF, NCEP/NCAR). This comparison indicates that the representation quality of surface parameters such as temperature and precipitation are highly correlated to the atmospheric circulation (500 hPa geopotential height) and its interannual variability (North Atlantic oscillation). The outputs of the three most suitable AOGCMs for present-day climate simulation are then used to assess the changes estimated by three IPCC greenhouse gas emissions scenarios (SRES) over the GrIS for the 2070–2099 period. Future atmospheric circulation changes are projected to dampen the zonal flow, enhance the meridional fluxes and therefore provide additional heat and moisture to the GrIS, increasing temperature over the whole ice sheet and precipitation over its northeastern area. We also show that the GrIS surface mass balance anomalies from the SRES A1B scenario amount to −300 km3/year with respect to the 1970–1999 period, leading to a global sea-level rise of 5 cm by the end of the 21st century. This work can help to select the boundaries conditions for AOGCMs-based downscaled future projections.

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See detailThe 1958–2009 Greenland ice sheet surface melt and the mid-tropospheric atmospheric circulation
Fettweis, Xavier; Mabille, Georges; Erpicum, Michel; Nicolay, Samuel; Van den Broeke, Michiel

in Climate Dynamics (2011), 36(1 (2011)), 139-159

In order to assess the impact of the mid-tropospheric circulation over the Greenland ice sheet (GrIS) on surface melt, as simulated by the regional climate model MAR, an automatic Circulation type classification (CTC) based on 500 hPa geopotential height from reanalyses is developed. General circulation correlates significantly with the surface melt anomalies for the summers in the period 1958–2009. The record surface melt events observed during the summers of 2007–2009 are linked to the exceptional persistence of atmospheric circulations favouring warm air advection. The CTC emphasizes that summer 500 hPa circulation patterns have changed since the beginning of the 2000s; this process is partly responsible for the recent warming observed over the GrIS.

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See detailEvaluation over Greenland of WRF with GC-NET observations (1995-2005) by comparison with 2 other RCMs
Sacré, Bernard; Fettweis, Xavier; Doutreloup, Sébastien; Franco, Bruno; van den Broeke, Michiel; Erpicum, Michel

Conference (2011)

In the context of climate change, the Greenland Ice Sheet (GrIS) plays an important role in sea level variation and oceanic thermohaline circulation changes. Unfortunately, Global Climate Models do not illustrate enough the characteristics of Greenland. To solve that, specific RCMs have been developed to take into account the features of polar regions. In this project, we compare three RCMs : the MAR model, the RACMO model and the Weather Research and Forecasting (WRF) model. WRF is an open source model developed by the Mesoscale and Microscale Meteorology Division of NCAR. We use here the standard WRF (version 3.2.1) and its polar optimization (called polar WRF). The MAR version tuned for the GrIS and coupled with a 1D surface scheme called SISVAT (for Soil Ice Snow Vegetation Atmosphere Transfer) is compared here. The version of RACMO is a specific version for the Greenland climate, RACMO2/GR. This model contains a special surface module for snow-ice treatment and other modifications concerning, for example, the surface turbulence heat flux or the surface roughness. The comparison is made on a domain centered on Greenland at a 25-km horizontal resolution over the 1995-2005 period when Automatic Weather Station (AWS) measurements are available from the Greenland Climate NETwork (GC-NET). Statistics (mean, bias, RMSE, correlation coefficient) are calculated for the near-surface temperature, surface pressure, 10m-wind speed and specific humidity for winter (October to April) and summer (May to September). In addition, the modeled snowfall are evaluated with ice core-based snow accumulation climatologies. Comparison shows a significant improvement from RCMs compared to the reanalyses (NCEP2 and ERA-INTERIM) in respect to the AWS measurements. RACMO and MAR seem to compare better with observations than WRF.

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See detailUsing a circulation type classification to analyse the general circulation over Greenland simulated by GCMs
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

Conference (2010, November 23)

Future projections of the Greenland ice sheet melt are mainly based on General Circulation Model (GCM) outputs. The atmospheric circulation type classification offers a unique opportunity for validating the GCM-based circulations. Six GCMs used in the last IPCC report are analysed here. A correlation-based classification is constructed for each model using daily geopotential height at 500 hPa over Greenland. It is applied to a dataset combining the GCM-based outputs (20C3M scenario) for the current climate and the NCEP-NCAR 1 reanalysis data over the period 1961-1990 allowing a direct comparison for each circulation type. Most of the analysed models are able to reproduce the main circulation types, but they fail to reproduce their frequencies because they underestimate the climate variability. In addition, some biases in the mean geopotential height remain. However, we use our atmospheric circulation type classification for analysing future projections made by GCMs. As for the 20th century climate, a combined classification is made integrating reanalysis data over 1971-1990, GCM-based outputs over 1971-1990 (using 20C3M scenario) and GCM-based outputs over 2046-2065 and 2081-2100 (using A1B scenario). No new circulation types are individualised knowing that the main changes are just a general increase of the geopotential height. Furthermore, the changes in frequency observed between the 20th century climate and the first future period (2046-2065) are of the same order than the uncertainties of the models for simulating the current climate by comparison with the reanalysis data. Therefore, the circulation type classification is a useful tool to give a precise analysis of the atmospheric circulation simulated by GCMs knowing that most of downscaling techniques are dependent on the general circulation simulated by the GCMs.

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See detailAnalysis of the atmospheric circulation simulated by GCMs over Greenland
Belleflamme, Alexandre; Fettweis, Xavier; Erpicum, Michel

Conference (2010, November 05)

The variability of the geopotential height at 500 hPa simulated by General Circulation Models (GCMs) over Greenland is evaluated using an atmospheric circulation type classification. The GCM outputs for the current climate (20C3M) are first compared to reanalysis data over 1961-1990. The comparison shows that most of them simulate well the main circulation types but fail to reproduce their frequencies because of underestimations of circulation variability and biases in the mean geopotential height. GCM-based future projections do not individualise new circulation types but show a general increase of the geopotential height. Based on this approach, the correlation between surface temperature and atmospheric circulation offers a new way for estimating the Greenland ice sheet melt.

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See detailHigh resolution modelling of the Greenland ice sheet surface mass balance using the regional climate model MAR coupled with a downscaling interface
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

Poster (2010, November 05)

We are developing a coupling interface downscaling the 25km-atmosphere fields simulated by the regional climate MAR (Modèle Atmosphérique Régional) model onto a 5km-grid in order to resolve the surface processes at high resolution with the SISVAT (Sea Ice Soil Vegetation Atmosphere Transfer) snow-ice module. This coupling interface improves the representation of the topography and ablation zone of the Greenland ice sheet (GrIS) in the MAR model, and therefore will provide higher resolution estimations of the GrIS surface mass balance (SMB) without additional computing time. By using outputs from previously-gauged global circulation models (GCM) as forcing fields, the MAR model coupled with the downscaling interface will then perform 5km future simulations of the GrIS SMB for different IPCC greenhouse gas emissions scenarios for the 21st century.

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See detailInterests of regional modelisation for wind power forecasting
Doutreloup, Sébastien; Fettweis, Xavier; Erpicum, Michel

Conference (2010, October 22)

European policies have decided to reduce the greenhouse gas emissions of 20% and to reach 20% of renewable power production by 2020. Increasing wind power is one of the numerous solutions to reach these goals. However, this kind of energy production depends on the meteorological conditions and gives it an intermittent behaviour. The wind speed variations cause voltage and frequency fluctuations that are unacceptable for the power grid. Therefore, forecasting production will become essential with the aim of integrating this kind of energy production into the power grid. We have developed and compared two forecasting models which give as outputs the wind power production every 15 minutes over the Belgian territory: the first one uses the outputs from the global model GFS (available at a horizontal resolution of 0.5° every 3h) and the second one uses the regional climate model WRF-NMM (using a horizontal resolution of 4km). Both of these models predict the wind speed and transform wind speed into wind power production, using a power curve which depends on the wind turbines and their characteristics. The first model using the GFS outputs is not precise enough in space and time to correctly forecast the wind speed in punctual wind farms. That is why we apply some specific tunings on these forecasts. These tunings depend on the air density, the wind direction and the stability of the air mass. The second model using the WRF-NMM outputs runs over the Belgian territory. Initial conditions are forced by the GFS outputs at 0.5° and WRF computes a physical based spatio-temporal downscaling of the meteorological variables. The outputs have a spatial resolution of 4 km and a time resolution of 15 minutes. Some tunings are also needed to adjust the wind power forecasts by comparison to the wind power observations. We present here some results of both models and the interest of using a regional model for more precise wind power forecasting.

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See detailModélisation à haute résolution de l'impact actuel et futur du réchauffement climatique sur le bilan de masse en surface de la calotte glaciaire du Groenland
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

Conference (2010, January 21)

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See detailMulti-Months Cycles Observed in Climatic Data
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

in Simard, Suzanne (Ed.) Climate Change and Variability (2010)

Climatic variations happen at all time scales and since the origins of these variations are usually of very complex nature, climatic signals are indeed chaotic data. The identification of the cycles induced by the natural climatic variability is therefore a knotty problem, yet the knowing of these cycles is crucial to better understand and explain the climate (with interests for weather forecasting and climate change projections). Due to the non-stationary nature of the climatic time series, the simplest Fourier-based methods are inefficient for such applications (see e.g. Titchmarsh (1948)). This maybe explains why so few systematic spectral studies have been performed on the numerous datasets allowing to describe some aspects of the climate variability (e.g. climatic indices, temperature data). However, some recent studies (e.g. Matyasovszky (2009); Paluš & Novotná (2006)) show the existence of multi-year cycles in some specific climatic data. This shows that the emergence of new tools issued from signal analysis allows to extract sharper information from time series. Here, we use a wavelet-based methodology to detect cycles in air-surface temperatures obtained from worldwide weather stations, NCEP/NCAR reanalysis data, climatic indices and some paleoclimatic data. This technique reveals the existence of universal rhythms associated with the periods of 30 and 43 months. However, these cycles do not affect the temperature of the globe uniformly. The regions under the influence of the AO/NAO indices are influenced by a 30 months period cycle, while the areas related to the ENSO index are affected by a 43 months period cycle; as expected, the corresponding indices display the same cycle. We next show that the observed periods are statistically relevant. Finally, we consider some mechanisms that could induce such cycles. This chapter is based on the results obtained in Mabille & Nicolay (2009); Nicolay et al. (2009; 2010).

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See detailA statistical validation for the cycles found in air temperature data using a Morlet wavelet-based method
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

in Nonlinear Processes in Geophysics (2010), 17

Recently, new cycles, associated with periods of 30 and 43 months, respectively, have been observed by the authors in surface air temperature time series, using a wavelet-based methodology. Although many evidences attest the validity of this method applied to climatic data, no systematic study of its efficiency has been carried out. Here, we estimate confidence levels for this approach and show that the observed cycles are significant. Taking these cycles into consideration should prove helpful in increasing the accuracy of the climate model projections of climate change and weather forecast.

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See detailCOST733CAT - a database of weather and circulation
Philipp, Andreas; Bartholy, Judit; Beck, Christoph; Erpicum, Michel; Esteban, Pere; Fettweis, Xavier; Huth, Radan; James, Paul; Jourdain, Sylvie; Kreienkamp, Frank; Krennert, Thomas; Lykoudis, Spyros; Michalides, Silas C.; Pianko-Kluczynska, Krystyna; Post, Piia; Álvarez, Domingo Rasilla; Schiemann, Reinhard; Spekat, Arne; Tymvios, Filippos S.

in Physics and Chemistry of the Earth (2010), 35(9-12), 360-373

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See detailEtude et modélisation des impacts hydrologiques de pluies exceptionnelles dans un environnement valloné et boisé
Deliège, Jean-François; Erpicum, Michel; Dassargues, Alain; Orban, Philippe; Billen, Roland; Hallot, Pierre; Petit, François; Van Campenhout, Jean; Levecq, Yannick; Pirotton, Michel; Archambeau, Pierre; Everbecq, Etienne; Magermans, Pol

Scientific conference (2009, September)

Le jeudi 29 mai 2008 a eu lieu en région liégeoise un événement pluvieux extrême qui a eu des conséquences (humaines et financières) douloureuses. Pour rappel, une pluie de courte durée, mais très intense (lame d’eau d’environ 90 litres par mètre carré en moins de 2 heures) sur le domaine du Sart Tilman a provoqué des inondations très soudaines (communément appelées « flash-floods ») aux abords des ruisseaux descendant du Sart Tilman vers la Meuse et l’Ourthe. Des évènements du même type ont eu lieu dans les semaines suivantes en région liégeoise (Remicourt, …). La méthodologie développée lors cette étude devait donc être transférable à d’autres applications. Le choix du Sart Tilman comme cas d’étude s’imposait cependant vu la bonne connaissance préliminaire du site par les équipes de l’ULg et la concentration des phénomènes extrêmes. Un tel évènement interpelle et amène à chercher à comprendre le phénomène, à le reproduire de façon théorique et à l’anticiper. Ainsi, à l’initiative de la Ministre de la recherche scientifique de la Communauté Française (Marie-Dominique Simonet), l’Aquapôle a fédéré un travail multidisciplinaire visant à décrire les mécanismes de ces événements extrêmes et à reproduire les impacts hydrologiques de ces pluies exceptionnelles à l’échelle locale, dans un environnement boisé et vallonné. Un des objectifs principaux de ce travail était d’obtenir une méthodologie incluant un modèle intégré permettant d’abord de représenter l’évènement, puis par la simulation de scénarios de tester l’effet spécifique de certains facteurs. En effet, outre la complexité de la dynamique météorologique qui les a générés (ces événements exceptionnels ont présenté des caractéristiques homogènes mais à une échelle très locale), les conséquences de l’évènement ont été le fruit de la combinaison complexe d’une série de facteurs environnementaux et humains : nature des sols, topographie locale, couverture végétale, ouvrages anthropiques et urbanisation, etc. De plus, pour effectuer une modélisation hydrologique physiquement basée et spatialement distribuée, il est nécessaire de disposer de nombreuses informations issues de sources différentes. L’approche pluridisciplinaire exigée pour la rencontre de ces phénomènes a pu être rapidement appréhendée à l’Aquapôle de l’Université de Liège. En particulier, l’existence de modèles compartimentaux intégrés a permis de tenir compte de la dynamique des bassins versants, de la nature hydrogéologique des sols et de la complexité des écoulements de surface et/ou sur l’axe hydraulique. Cette approche de modélisation opérationnelle et pragmatique a tout d’abord nécessité la collecte et la préparation d’un grand nombre de données (dans les environnements cartographiques appropriés) afin d’alimenter les modèles et de créer des bases de données. Ce volet a impliqué un noyau d’équipes composées de topo-climatologues, de topographes, d’hydrauliciens, d’hydrogéologues et d’intégrateurs numériques de façon à prendre en considération l’ensemble des processus et paramètres pertinents à l’atteinte de l’objectif visé. Sur base de la description des processus et de leurs dynamiques spatiale et temporelle ayant abouti à ces catastrophes, l’Aquapôle a pu reproduire et mettre en évidence les événements grâce à des outils de simulations numériques s’appuyant sur une description fine de la météorologie et de la topographie locale, des ouvrages d’art existants et des spécificités locales de toute nature (anthropiques et naturelles). Le dernier volet de cette étude a été dédié à l’élaboration intégrée de scénarios de simulation pour l’utilisation du modèle WOLF HYDRO : un modèle hydrologique spatialement et temporellement distribué qui est principalement développé pour représenter les transferts quasi horizontaux prépondérants en périodes de crues. Son approche physiquement basée lui permet d’utiliser au mieux les différentes informations disponibles. Il a été utilisé dans cette étude, en s’appuyant sur les informations générées par les autres équipes. Pour les trois bassins versants étudiés, de caractéristiques sensiblement différentes, la méthodologie employée permet d’aboutir à des hydrogrammes réalistes pour l’épisode du 29 mai 2008. Des scénarios multiples ont également permis de vérifier la sensibilité du modèle, de tester l’influence d’aménagements potentiels sur le bassin versant (changements d’occupation des sols, création de bassins d’orage, …) et de fournir des résultats pour des pluies de récurrences fixées d’une durée proche de l’événement principal. Les observations réalisées lors de l’événement et les résultats de la modélisation permettent de conclure au fait que l’événement de mai 2008 est véritablement extrême et qu’aucun équipement raisonnable n’aurait pu aboutir à un affaiblissement significatif des débits observés aux exutoires des ruisseaux. Les pics de crues sont en effet parfois proches du double de ceux observés pour une crue bi-centennale. Ainsi, lors d’un tel événement, seul un aménagement prudent de l’habitat aux abords des ruisseaux peut amener à une réduction des dommages matériels. En effet, la délivrance de permis d’urbanisme sur le cours d’eau ou à son voisinage immédiat aggrave les conséquences de ces phénomènes exceptionnels. Enfin, conformément à la notification du Gouvernement Wallon (séance du 3 juin 2009), les résultats de la recherche FL², confiée par la Communauté Française à l’ULg, seront intégrés dans les travaux du GTI (Groupe Transversal Inondations). Ces résultats ont fait l’objet d’une présentation collégiale au GTI le 5 octobre 2009 et d’une présentation à destination des communes et d’un public large et ouvert le 19 novembre 2009.

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See detailEtude et modélisation des impacts hydrologiques de pluies exceptionnelles dans un environnement vallonné et boisé
Deliège, Jean-François; Erpicum, Michel; Dassargues, Alain; Orban, Philippe; Billen, Roland; Hallot, Pierre; Petit, François; Van Campenhout, Jean; Levecq, Yannick; Pirotton, Michel; Archambeau, Pierre; Everbecq, Etienne; Magermans, Pol

Report (2009)

Le jeudi 29 mai 2008 a eu lieu en région liégeoise un événement pluvieux extrême qui a eu des conséquences (humaines et financières) douloureuses. Pour rappel, une pluie de courte durée, mais très intense (lame d’eau d’environ 90 litres par mètre carré en moins de 2 heures) sur le domaine du Sart Tilman a provoqué des inondations très soudaines (communément appelées « flash-floods ») aux abords des ruisseaux descendant du Sart Tilman vers la Meuse et l’Ourthe. Des évènements du même type ont eu lieu dans les semaines suivantes en région liégeoise (Remicourt, …). La méthodologie développée lors cette étude devait donc être transférable à d’autres applications. Le choix du Sart Tilman comme cas d’étude s’imposait cependant vu la bonne connaissance préliminaire du site par les équipes de l’ULg et la concentration des phénomènes extrêmes. Un tel évènement interpelle et amène à chercher à comprendre le phénomène, à le reproduire de façon théorique et à l’anticiper. Ainsi, à l’initiative de la Ministre de la recherche scientifique de la Communauté Française (Marie-Dominique Simonet), l’Aquapôle a fédéré un travail multidisciplinaire visant à décrire les mécanismes de ces événements extrêmes et à reproduire les impacts hydrologiques de ces pluies exceptionnelles à l’échelle locale, dans un environnement boisé et vallonné. Un des objectifs principaux de ce travail était d’obtenir une méthodologie incluant un modèle intégré permettant d’abord de représenter l’évènement, puis par la simulation de scénarios de tester l’effet spécifique de certains facteurs. En effet, outre la complexité de la dynamique météorologique qui les a générés (ces événements exceptionnels ont présenté des caractéristiques homogènes mais à une échelle très locale), les conséquences de l’évènement ont été le fruit de la combinaison complexe d’une série de facteurs environnementaux et humains : nature des sols, topographie locale, couverture végétale, ouvrages anthropiques et urbanisation, etc. De plus, pour effectuer une modélisation hydrologique physiquement basée et spatialement distribuée, il est nécessaire de disposer de nombreuses informations issues de sources différentes. L’approche pluridisciplinaire exigée pour la rencontre de ces phénomènes a pu être rapidement appréhendée à l’Aquapôle de l’Université de Liège. En particulier, l’existence de modèles compartimentaux intégrés a permis de tenir compte de la dynamique des bassins versants, de la nature hydrogéologique des sols et de la complexité des écoulements de surface et/ou sur l’axe hydraulique. Cette approche de modélisation opérationnelle et pragmatique a tout d’abord nécessité la collecte et la préparation d’un grand nombre de données (dans les environnements cartographiques appropriés) afin d’alimenter les modèles et de créer des bases de données. Ce volet a impliqué un noyau d’équipes composées de topo-climatologues, de topographes, d’hydrauliciens, d’hydrogéologues et d’intégrateurs numériques de façon à prendre en considération l’ensemble des processus et paramètres pertinents à l’atteinte de l’objectif visé. Sur base de la description des processus et de leurs dynamiques spatiale et temporelle ayant abouti à ces catastrophes, l’Aquapôle a pu reproduire et mettre en évidence les événements grâce à des outils de simulations numériques s’appuyant sur une description fine de la météorologie et de la topographie locale, des ouvrages d’art existants et des spécificités locales de toute nature (anthropiques et naturelles). Le dernier volet de cette étude a été dédié à l’élaboration intégrée de scénarios de simulation pour l’utilisation du modèle WOLF HYDRO : un modèle hydrologique spatialement et temporellement distribué qui est principalement développé pour représenter les transferts quasi horizontaux prépondérants en périodes de crues. Son approche physiquement basée lui permet d’utiliser au mieux les différentes informations disponibles. Il a été utilisé dans cette étude, en s’appuyant sur les informations générées par les autres équipes. Pour les trois bassins versants étudiés, de caractéristiques sensiblement différentes, la méthodologie employée permet d’aboutir à des hydrogrammes réalistes pour l’épisode du 29 mai 2008. Des scénarios multiples ont également permis de vérifier la sensibilité du modèle, de tester l’influence d’aménagements potentiels sur le bassin versant (changements d’occupation des sols, création de bassins d’orage, …) et de fournir des résultats pour des pluies de récurrences fixées d’une durée proche de l’événement principal. Les observations réalisées lors de l’événement et les résultats de la modélisation permettent de conclure au fait que l’événement de mai 2008 est véritablement extrême et qu’aucun équipement raisonnable n’aurait pu aboutir à un affaiblissement significatif des débits observés aux exutoires des ruisseaux. Les pics de crues sont en effet parfois proches du double de ceux observés pour une crue bi-centennale. Ainsi, lors d’un tel événement, seul un aménagement prudent de l’habitat aux abords des ruisseaux peut amener à une réduction des dommages matériels. En effet, la délivrance de permis d’urbanisme sur le cours d’eau ou à son voisinage immédiat aggrave les conséquences de ces phénomènes exceptionnels. Enfin, conformément à la notification du Gouvernement Wallon (séance du 3 juin 2009), les résultats de la recherche FL², confiée par la Communauté Française à l’ULg, seront intégrés dans les travaux du GTI (Groupe Transversal Inondations). Ces résultats ont fait l’objet d’une présentation collégiale au GTI le 5 octobre 2009 et d’une présentation à destination des communes et d’un public large et ouvert le 19 novembre 2009.

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See detailGreenland ice sheet projections from IPCC AR4 global models
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel; Nicolay, Samuel

Poster (2009, April)

The atmosphere-ocean general circulation models (AOGCMs) used for the IPCC 4th Assessment Report (IPCC AR4) are evaluated for the Greenland ice sheet (GrIS) current climate modelling. The most efficient AOGCMs are chosen by comparison between the 1970-1999 outputs of the Climate of the twentieth Century experiment (20C3M) and reanalyses (ECMWF, NCEP/NCAR). This comparison reveals that surface parameters such as temperature and precipitation are highly correlated to the atmospheric circulation (500 hPa geopotential height) and its interannual variability (North Atlantic oscillation). The outputs of the three most efficient AOGCMs are then used to assess the changes planned by three IPCC greenhouse gas emissions scenarios (SRES) for the 2070-2099 period. Future atmospheric circulation changes should dampen the west-to-east circulation (zonal flow) and should enhance the Meridional Overturning Circulation (MOC). As a consequence, this provides more heat and moisture to the GrIS, increasing temperature on the whole ice sheet and precipitation on the north-eastern region. It is also shown that the GrIS surface mass balance (SMB) anomalies from the SRES A1B scenario are about -300 km³/yr with respect to the 1970-1999 period, leading to 5 cm of global sea-level rise (SLR) for the end of the 21st century. This work helps to choose the boundaries conditions for AOGCMs downscaled future projections.

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See detailCycles in the Temperature Data Are Induced by the Sun
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

Poster (2009, April)

The presence of two cycles of period of 30 and 42 months approximatively has been observed in temperature records and climatic indices. Moreover, it has been shown that these cycles are statistically significant. Here we outline the role played by the Sun in the presence of these cycles, observed in time series. To do so, we use IPCC AR4 climatic models, sunspot number data and the Morlet wavelet method.

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See detailConfidence Levels for the Cycles Found in Air Temperature Data
Mabille, Georges; Fettweis, Xavier; Erpicum, Michel; Nicolay, Samuel

Poster (2009, April)

Recently, new cycles have been observed in air temperature data and proxy series using a wavelet-based methodology. Although many evidences attest the validity of this method applied to climatic data, no systematic study of its efficiency has been carried out. Here, we estimate the confidence levels for this approach and show that the observed cycles are significant.

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See detailCycles found in air temperature data and proxy series using the Morlet wavelet method
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

Scientific conference (2009, February 25)

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See detailGreenland ice sheet surface mass balance projections from IPCC AR4 global models
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

Poster (2009, January 28)

Results from atmosphere-ocean general circulation models (AOGCM's) for the IPCC 4th Assessment Report are used to investigate surface mass balance (SMB) future projections of the Greenland ice sheet (GrIS). The most efficient models for the GrIS climate modeling are chosen by comparison between the 1970-1999 outputs (averages and trends) from the Climate of the twentieth Century Experiment (20C3M) and reanalyses (ECMWF, NCEP) as well as observations (ice core measurements). The outputs from these most efficient models are after used to assess changes planned by the IPCC greenhouse gas emissions scenarios (SRES) for the 2070-2099 period. The GrIS SMB projections are estimated from changes in precipitation and temperatures from these AOGCM's outputs. However, large uncertainties remain in these SMB projections based on simplified physics and huge model outputs. High resolution simulations made with regional models (which simulate explicitly the SMB by taking into account the surface feedbacks) forced at their boundaries by a GrIS well-adapted AOGCM could bring more precise brief replies.

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See detailNew cycles found in air temperature data and proxy series using the Morlet wavelet method
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

Conference (2009, January 13)

We use the wavelet transform to detect cycles in air temperature data and proxy series

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See detailEstimation de la transparence de l'atmosphère par ciel clair à la Station Scientifique des Hautes-fagnes (SSHF), Mont Rigi, Belgique. Comparaison avec la Station d'Uccle-Bruxelles (IRM)
Dury, Marie; Ginion, Serge; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (2009), 51(2008), 5-16

This paper deals with the study of the transparency of the atmosphere on clear sky at the Mont Rigi (Belgian Hautes-Fagnes) with the aim of underlining the particularities of the air composition in the Hautes-Fagnes region and quantifying its influence on global solar radiation. We used the following data: solar elevation, water vapor content (characterized by atmospheric water depth) and solar extraterrestrial irradiation at the top of the atmosphere. Due to a lack of direct information about atmospheric pollution, we compared global radiation received at the Hautes-Fagnes scientific station (SSHF) on clear sky with that stored in the same conditions in Uccle (Brussels), the Belgian reference station (Royal meteorological institute, RMI) and urban area.

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See detail30 and 43 months period cycles found in air temperature time series using the Morlet wavelet
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

in Climate Dynamics (2009), 33

A wavelet-based methodology is applied to relevant climatic indices and air temperature records and allow to detect the existence of unexpected cycles. The scale spectrum shows the presence of two cycles of about 30 and 43 months, respectively, in the air–temperature time series, in addition to the well-known cycles of 1 day and 1 year. The two cycles do not affect the globe uniformly: some regions seem to be more influenced by the period of 30 months (e.g. Europe), while other areas are affected by the period of 43 months (e.g. North-West of the USA). Similar cycles are found in the indices and the regions influenced by these indices: the NAO index and the Western Europe display a cycle of 30 months, while the cycle of 43 months can be found in the ENSO index and in regions where it is known to have an impact.

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See detailAnalysis of climatic conditions of wildfires in Belgium with an automatic daily atmospheric circulation patterns classification
Erpicum, Michel; Fettweis, Xavier; Mabille, Georges

Conference (2008, October 02)

An automatic daily atmospheric circulation patterns classification was built using the geopotential heights of 850 hPa level from the ECMWF (re)analysis over the period 1958-2007. The classification is based on a similarity index between two 850hPa geopotential maps centred on Belgium, taking into account the slope difference between both daily geopotential surfaces as well as the absolute geopotential difference between both surfaces. Wildfire occurrences are analysed in April and September together with monthly frequencies and persistences of daily atmospheric circulation patterns types as well as with monthly variability of weather climate conditions.

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See detailNew cycles found in air temperature data and proxy series
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

Conference (2008, October 01)

We apply the wavelet transform tool to detect unsuspected cycles in several climatic time series

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See detailSolar activity in connection with a 2.5 years periode cycle in air temperature time series using the Morlet wavelet method
Nicolay, Samuel; Mabille, Georges; Fettweis, Xavier; Erpicum, Michel

Conference (2008, April 17)

The Morlet wavelet is applied to air temperature time series obtained from several weather stations and reveals the existence of a period cycle of 20-30 months since 1950, with an estimated amplitude of 0.5 C. The origin of this period is investigated by computing the scale spectra associated to the principal indices that characterize air mass flows in the troposphere and the stratosphere, as well as the signals related to the sunspot number and the solar flux. Each analysed signal shows this period of approximatively 2.5 years. This suggests that the 2.5 years-cycle could be resulted from the solar activity.

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See detailAutomatic 1958-2007 daily weather pattern classification applied to an analysis of climatic conditions of wildfires in eastern Belgium
Erpicum, Michel; Fettweis, Xavier; Mabille, Georges; François, Louis

Poster (2008, April)

The daily atmospheric circulation patterns classification is founded on a 100 km regular grid centred on Belgium. The geopotential heights of 500, 850 and 1000 hPa levels were extracted <br />from the ERA-40 database on the period 1958-2002 and from ECMWF operational analysis until the end of year 2007. The classification was based on a similarity index calculated on the orientation of exaggerated slopes of different daily geopotential fields. Wildfire occurrences were analyzed in April and September (which are the two months with the most frequent wildfire-days in Belgium) together with monthly frequencies and persistences of daily atmospheric circulation pattern classes as well as with yearly variability of weather climate conditions.

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See detailLast century Greenland ice sheet surface mass balance projections from IPCC AR4 global models
Franco, Bruno; Fettweis, Xavier; Erpicum, Michel

Poster (2008, April)

Results from atmosphere-ocean general circulation models (AOGCM's) for the IPCC 4th Assessment Report are used to investigate surface mass balance (SMB) future projections of the Greenland ice sheet (GrIS). The most efficient models for the GrIS climate modeling are chosen by comparison between the 1970-1999 outputs (averages and trends) from the 20C3M Experiment outputs, and the reanalyses (ECMWF, NCEP) as well as climatologies. The SMB is estimated from the summer temperature (from which is deduced the run-off) and annual snowfall from the well-adapted AOGCM's. It is validated with 1970-1999 results from the regional climate model MAR by interpolating the AOGCM's outputs on the MAR grid. However, large uncertainties remain in these SMB projections due to the simplified physic and coarse AOGCM's resolution. High resolution simulations made with the MAR model (which simulates explicitly the SMB by taking into account the surface feedbacks) forced at its boundaries by a GrIS well-adapted AOGCM could bring more precise brief replies.

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See detailEstimation of the 1900-2100 Greenland ice sheet surface mass balance
Fettweis, Xavier; Hanna, E.; Gallée, H.; Erpicum, Michel

Conference (2008, April)

See detailClimatologie - Topoclimatologie
Erpicum, Michel

Book (2008)

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See detailCirculations atmosphériques et anomalies de fonte à la surface de la calotte glaciaire du Groenland
Fettweis, Xavier; Mabille, Georges; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (2008), 51

With the aim to study the impact of the 500hPa general circulation on the Greenland ice sheet surface melt simulated by the regional climate model MAR, we developed a new Circulation Type Classification (CTC) based on the 500hPa geopotential height from the ECMWF (re)analysis over the period 1958-2007. This CTC shows that the dominant mode of the regional atmospheric variability around the Greenland is linked to the North Atlantic Oscillation (NAO) and that the surface anomalies are highly correlated to the general circulation. It explains also why a record surface melt was observed during the summer 2007. The 27th August of 2003, where the temperature was 10°C higher than the normal, is the consequence of an almost unique 500 hPa circulation in the 50 last years.

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See detailEstimation of the Greenland ice sheet surface mass balance for the 20th and 21st centuries
Fettweis, Xavier; Hanna, Edward; Gallée, Hubert; Huybrechts, Philippe; Erpicum, Michel

in Cryosphere (2008), 2

Results from a regional climate simulation (1970–2006) over the Greenland ice sheet (GrIS) reveals that more than 97% of the interannual variability of the modelled Surface Mass Balance (SMB) can be explained by the GrIS summer temperature anomaly and the GrIS annual precipitation anomaly. This multiple regression is then used to empirically estimate the GrIS SMB since 1900 from climatological time series. The projected SMB changes in the 21st century are investigated with the set of simulations performed with atmosphere-ocean general circulation models (AOGCMs) of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). These estimates show that the high surface mass loss rates of recent years are not unprecedented in the GrIS history of the last hundred years. The minimum SMB rate seems to have occurred earlier in the 1930s and corresponds to a zero SMB rate. The AOGCMs project that the SMB rate of the 1930s would be common at the end of 2100. The temperature would be higher than in the 1930s but the increase of accumulation in the 21st century would partly offset the acceleration of surface melt due to the temperature increase. However, these assumptions are based on an empirical multiple regression only validated for recent/current climatic conditions, and the accuracy and time homogeneity of the data sets and AOGCM results used in these estimations constitute a large uncertainty.

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See detailContribution à l'étude du climat de trois cavités souterraines belges
Piron, Julie; Erpicum, Michel; Ek, Camille; Godissart, Jean; Willems, Luc

in Bulletin de la Société Royale Belge d'Études Géologiques et Archéologiques (2007), XLVI

Some temperature and CO2 measures have been made for one year in the cave of Ramioul and in the cave of Comblain-au-Pont, and for six months in the underground quarry of Petit-Lanaye inférieure. Temperature has been measured by dataloggers. These measures and the comparison between the different caves contributed to a better understanding of their climates. In the cave of Ramioul, closed by non insulated doors, the air movements are relatively low but there are some heat exchanges between the outside and inside air by conduction through the doors. The cave can be divided into two parts each with a different climatic behaviour. High and dangerous CO2 rates have already been measured in this cave. Rates fluctuate in an irregular way and without any connection with the natural seasonal cycle, and the CO2 origins stay uncertain. The cave of Comblain-au-Pont can be divided into two major parts: one enclosed and the other ventilated. The ventilated region is a “wind tube” during the winter, but it doesn’t reverse in the summer. On a larger scale, this region can be considered as a cold air trap despite its two exits, since it has a descendant morphology. <br />In the underground carry of Petit-Lanaye inférieure, the low number of data doesn’t allow a complete diagnosis of the climate organisation, but can give a first idea for the summer period. We can already distinguish some parts that are more or less influenced by the outside temperature fluctuations, probably in relation with some air movements which organised <br />themselves in a complex way in the labyrinthic galleries network.

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See detailHistory and clinical features of atypical myopathy in horses in Belgium (2000-2005)
Votion, D. M.; Linden, Annick; Saegerman, Claude; Engels, Patrick; Erpicum, Michel; Thiry, Etienne; Delguste, Catherine; Rouxhet, Serge; Demoulin, Vincent; Navet, Rachel; Sluse, Francis; Serteyn, Didier; Van Galen, Gaby; Amory, Hélène

in Journal of Veterinary Internal Medicine (2007), 21(6, Nov-Dec), 1380-1391

Background: The emergent nature of atypical myopathy or atypical myoglobinuria (AM) necessitates precise description of its clinical and epidemiologic features. Purpose: To define key features of AM to help practitioners recognize the disease and to advise owners to take preventive measures. Animals: Belgian cases of AM confirmed by histology (CC horses; n = 57) from autumn 2000 to spring 2005 were included in the study. Co-grazing horses (Co-G horses; n = 77) that remained free of any abnormal clinical signs constituted a control croup. Methods: History, environmental characteristics, clinical signs, and laboratory results associated with AM were determined by a retrospective case series study. Results: Young horses in poor or normal body condition were found to be at risk for AM. Pastures were characterized by poor natural drainage and vegetation of low nutritional value. Features of AM were seasonal occurrence, apparent link with weather conditions fie, lack of solar radiation with no heavy frost and an excess of precipitation or relative humidity), sudden onset of clinical signs, and rapid death. Evaluation of serum creatine kinase activity indicated severe muscle destruction in CC horses and subclinical disease in a few Co-G horses. Conclusions: The association of AM with specific environmental conditions and individual animals suggests that young horses should not be pastured on bare premises subject to humidity when the weather has been very wet and cold for several days. Management of AM outbreaks should include control of Co-G horses who are apparently healthy.

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See detailVariabilité spatio-temporelle de l’albédo. Analyse menée à la résolution métrique
Van Durme, G.; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (2005), 46

Albedo is a climatic factor that has been barely studied and thus is badly understood. However, it has a certain influence on our climate. This influence is especially visible in case of land use changes, such as deforestation. The aim of the study presented in this paper is to increase the current knowledge on albedo and the factors that influence it. To achieve this, a field survey was conducted. Not all factors could be studied during the field campaign; among those that were effectively observed, the most important ones – those that were responsible for the biggest changes in albedo – were the development of vegetation, the presence of snow and the daily variation of the height of the sun.

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See detailModélisation de la distribution spatiale des précipitations en Sicile.
Cornet, Yves; Fitschy, C.; Gobbato, O.; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (2005), 46

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See detailBrouillards et mauvaises visibilités en Belgique : Analyse menée à partir des observations météorologiques effectuées dans les aéroports civils
Erpicum, Michel; De Swert; Nyssen, Thierry; Thibaut, Eric

in Publications de l'Association Internationale de Climatologie (2005), 18

See detailReal-time regional automatic mapping of nocturnal winter road temperatures. Application of a methodology of analogous situations. The case of the Walloon Region (Belgium). American Meteorological Society
Erpicum, Michel; Frédéric, Marc; Nyssen, Th.; Mabille, G?.; Litt, S.

Scientific conference (2005)

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See detailDiscrimination des effets radiatifs et des effets advectifs à partir des observations de températures du réseau météo-routier de Wallonie
Erpicum, Michel

in Norois (2004), 191(2004/2), 105-11074-75

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See detailQuel est le "noyau dur" de la formation en géographie? Le point de vue d'un géographe climatologue.
Erpicum, Michel

in Géographes Associés (2003), 27

Which geograpry to teach tomorrow at university? The point of view of a geographer working in climatology and topoclimatology.

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See detailLa climatologie
Erpicum, Michel; Alexandre, Jean

in Bulletin de la Société Géographique de Liège (2003), 43(2003), 79-88

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See detailLa géographie appliquée à l’université de Liège
Binard, Marc; Devillet, Guénaël; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (2003), 43

Historic of the applied geography within the various units of the Geographic Department of the University of Liège (Belgium)

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See detailThe Sahelian drought may have ended during the 1990s
Ozer, Pierre; Erpicum, Michel; Demarée, Gaston; Vandiepenbeeck, Marc

in Hydrological Sciences Journal (2003), 48(3), 489-492

The severe drought that affects the Sahel since the late 1960s has been very closely studied and monitored during the last three decades. Recently, after several wet years, it was questioned from a statistical point of view whether the drought was over. The conclusions of a recent study were that the rainfall deficit was not over at the end of 2000 and that the drought continues. The analysis of the change points in the station rainfall time series suggests differentiating these findings. There is now growing evidence that there is a potential shift towards a more humid state. However, the present analysis shows that the assumption that a significant increase in rainfall may have occurred around the early 1990s could only be verified at the customary confidence level in about 10 years from now.

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See detailConditions radiatives nocturnes hivernales et température de la chaussée : l’exemple de la station météoroutière de Berloz (Belgique)
Erpicum, Michel; Alexandre, Jean; Etienne, Hugues; Frederic, Marc; Mabille, Georges; Nyssen, Thierry

in Publications de l'Association Internationale de Climatologie (2000), 13

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See detailObservation des lithométéores pour le suivi de la désertification en Afrique de l’Ouest. Mise au point sur le recours aux observations synoptiques
Erpicum, Michel; Ozer, Pierre

in Publications de l'Association Internationale de Climatologie (1999), 12

See detailClimat - Klimaat
Alexandre, Jean; Erpicum, Michel; Vandiepenbeeck, Marc

Cartographic material (1999)

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See detailLa dispersion de l’habitat en zone rurale : source de contraintes pour la collectivité et de surcoût du service d’hiver d’entretien routier
Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1998), 34

See detailConséquences de la sécheresse sur la longueur et l’amplitude de la saison des pluies au Niger
Daouda, M.; Ozer, Pierre; Erpicum, Michel

in DEMAREE, Gaston; Alexandre, Jean; DE DAPPER, Morgan (Eds.) Tropical climatology, meteorology and hydrology : in memoriam Franz Bultot (1924-1995). (1998)

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See detailOverhead line galloping : Field experience during one event in Belgium on February 13th, 1997
Lilien, Jean-Louis; Erpicum, Michel; Wolfs, M.

in IWAIS '98, International Conference, Reykjavik,June 1998, Proceedings (1998)

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See detailPrécipitations atmosphériques et altitude. Prélude à une cartographie des montants annuel et mensuels en Belgique
Alexandre, Jean; Erpicum, Michel; Mabille, Georges; Cornet, Yves

in Publications de l'Association Internationale de Climatologie (1998), 11

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See detailAnalyse du refroidissement après minuit de la température de la chaussée en Wallonie
Erpicum, Michel; Mabille, G.; Marczuk, S.

in Publications de l'Association Internationale de Climatologie (1998), 11

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See detailA dustfall event in November 1996 in Genoa, Italy.
Ozer, Pierre; Erpicum, Michel; Cortemiglia, Gian Camillo; Lucchetti, Gabriella

in Weather (1998), 53(5), 140-145

See detailClimatology
Erpicum, Michel

in Bulletin de la Société Belge d'Études Géographiques (1996), 64 (2)

See detailLes tempêtes (tempêtes extratropicales, cyclones tropicaux et tornades)
Erpicum, Michel; Van Hoof, Th.

in Le point sur le I de Géographie (Soc géogr de Liège) (1996), 4

See detailEvolution chronologique des précipitations dans le Sud-Est du Zaïre. Comparaison avec celle des pays voisins
Kalombo, K.; Erpicum, Michel; Assani, A.

in Publications de l'Association Internationale de Climatologie (1996), 9

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See detailVariations interannuelles des précipitations mensuelles et leur répartition spatiale en Belgique
Alexandre, Jean; Mabille, Georges; Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1996), 9

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See detailLes fondements de l'analyse numérique de photos prises au fisheye pour des besoins topoclimatologiques
Cornélis, Bernard; Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1995), 8

Fisheye pictures are frequently used in forestry and in ecology for canopy measurements. In climatology, it seems that they have only been used for illustration purposes. In fact, fisheye pictures are rich in climatological information. Digital fisheye image processing can be used for applied climatology as well as for topoclimatological studies. It allows the quantification of insolation, diffuse radiation, sky-view factor,.… In other words, it provides an objective assessment of the exposure of a site or of a measuring device. This article introduces the basis for digital fisheye image processing. The possibilities offered by this tool will be illustrated with sunshine measurements in an urban environment.

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See detailMéthodologie pour une meilleure représentation spatio-temporelle des fluctuations pluviométriques observées au Niger depuis 1905
Ozer, Pierre; Erpicum, Michel

in Sécheresse (1995), 6(1), 103-108

The fluctuations of annual precipitation observed in Niamey and Zinder (Niger) since the turn of the century warranted a comparison of rainfall maps and rainy-season characteristics between 1950-1967 (period of high rainfall) and 1968-1985 (period of low rainfall). Calculating two specific annual spatiotemporal rainfall profiles provided precisions as to the irregular and heterogeneous advance of the drought through Niger.

See detailLes échelles spatiales du climat
Tricot, C.; Erpicum, Michel

in Dachelet, A.; Hallet, C.; Petitjean, M. (Eds.) Etat de l'Environnement Wallon - 1994 (Vol 1) (1995)

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See detailThermographie routière nocturne de la Région Wallonne : méthodologie, présentation des résultats et intérêts de l'approche topoclimatologique
Funcken, Ph.; Erpicum, Michel; Frédéric, Marc; Mabille, G.

in Publications de l'Association Internationale de Climatologie (1995), 8

See detailLe climat de la région Wallonne : les normales climatologiques et leurs variabilités spatiotemporelles
Vandiepenbeeck, M.; Tricot, C.; Joukoff, A.; Erpicum, Michel

in Petitjean, M.; Dachelet, A.; Hallet, C. (Eds.) Etat de l'Environnement Wallon - 1994 (Vol 1) (1995)

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See detailSuivi de la saison des pluies 1991-1992 en Afrique équatoriale à l'aide des indicateurs Météosat "occurrences des nuages à sommet froid et températures de brillance maximum de surface
Kalombo, K.; Lahuec, J. P.; Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1995), 8

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See detailMise au point d’une classification automatique des cartes synoptiques d’altitude et application à l’étude des incendies de forêts
Mabille, Georges; Geron, Jean-Marc; Funcken, Philippe; Frédéric, Marc; Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1995), 8

See detailClimatological Secondary Meteosat Image : Analysis proposed to earth observation scientists
Erpicum, Michel

in Earth observation (1994), 3

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See detailAnomalie pluviométrique négative sur le Sud-est du Zaïre en janvier 1992
Kalombo, K.; Erpicum, Michel; Lahuec, J. P.

in Publications de l'Association Internationale de Climatologie (1994), 7

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See detailSuivi satellitaire (Météosat 5) de la situation météorologique des 21, 22, 23 septembre 1992 sur l'Europe occidentale et le Proche Atlantique
Erpicum, Michel

in Revue de Géographie de Lyon (1993), 68

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See detailTypes de circulation atmosphériques, advection des masses d'air et variations climatiques: Le cas des hivers doux et des hivers rudes récents en Belgique
Erpicum, Michel; Mabille, Georges; Alexandre, Jean

in Publications de l'Association Internationale de Climatologie (1993), 6

In Belgium, air masse advections -as it appears at 850 hPa level- are very important for the explanation of the surface air temperature of mild winters. Nevertheless in case of severe winters, radiative conditions observed at tropospheric lower level and horizontal motion of very thin air masses (below 850 hPa level) seem to be more important for the explanation of ground level temperature.

See detailLe climat
Alexandre, Jean; Erpicum, Michel; Vernemmen, C.

in Denis, J. (Ed.) Géographie de la Belgique (1992)

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See detailAdvection des masses d'air et température de l'air près du sol : recherche d'une méthode d'analyse
Erpicum, Michel; Mabille, Georges; Alexandre, Jean

in Publications de l'Association Internationale de Climatologie (1992), 5

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See detailLa topoclimatologie, un outil au service de l'agronomie. Exemples pris en Belgique
Erpicum, Michel

in Bulletin des Recherches Agronomiques de Gembloux (1991), 26(1)

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See detailComparaison des températures mesurées en Belgique dans un site urbain (Uccle) et un site rural (Thimister) : Impact d'un changement de site sur une série de données thermométriques (Thimister)
André, Pascale; Mabille, Georges; Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1991), 4

A comparative study of long temperature series in an urban station and in a rural station situated in Belgium determine if warming detected in the urban station or temporay change in the rural station can be generalized or not into the country.

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See detailVariabilité spatiale et temporelle de l'enneigement du sol en Belgique
Erpicum, Michel; Mabille, Georges; Vlassis, Patricia

in Publications de l'Association Internationale de Climatologie (1991), 4(1991), 267-273

See detailAfrique centrale : géomorphologie et géologie récente (hommage au Professeur Alexandre)
Petit, François; Erpicum, Michel; Grimberieux, J.; Laurant, A.

Book published by Société Géographique de Liège (1991)

See detailAfrique centrale : géomorphologie et géologie récente
Petit, François; Erpicum, Michel; Grimberieux, J.; Laurant, A.

Book (1991)

See detailSurveillance des variations de la nappe d'eau superficielle en Fagnes de Duret et du Setay
Erpicum, Michel; Streel, Maurice; Groulard, J. M.; Crahay, M.

in Hautes Fagnes (1991), 203

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See detailCaractérisation des anomalies pluviométriques de la saison des pluies 1989-1990 dans le Sud-Est du Zaïre
Kalombo, K.; Ntombi, M. K.; Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1991), 4

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See detailLes modelés éoliens de la région de Zinder (Niger méridional): Etude de photo-géomorphologie. Note préliminaire. Apports de la télédétection à la lutte contre la sécheresse
Karimoune, Salifou; Ozer, André; Erpicum, Michel

in Actualité Scientifique Univ. Francophones (1990)

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See detailVariations saisonnières du profil vertical du vent dans la région de Lubumbashi (Haut-Shaba, Zaïre)
Erpicum, Michel; Ntombi, M. K. M.

in Publications de l'Association Internationale de Climatologie (1990), 3

This study, based on 450 aerological soundings from 1957 to 1982 at Lubumbashi, analyses the seasonal variations of the wind vertical stratification of the troposphere. The vertical aerologic profile is more complex during the dry season than during the rainy season.

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See detailAnalyse de la variabilité spatiale de la température à l'aide de transects mobiles ( application en topoclimatologie)
Erpicum, Michel

in Publications de l'Association Internationale de Climatologie (1989), 2

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See detailSurveillance des variations de la nappe d'eau superficielle en Fagnes de Duret et du Setay
Erpicum, Michel; Streel, Maurice; Groulard, J. M.; Crahay, M.

in Hautes Fagnes (1989), 195

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See detailContribution to the development of an erosivity index adapted to the prediction of erosion in Belgium
Sinzot, Anne; Bolline, Arthur; Laurant, Adrien; Erpicum, Michel; Pissart, Albert

in Earth Surface Processes and Landforms (1989), 14

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See detailVariabilité des potentialités climatiques des régions touristiques. L'exemple de l'espace côtier méditerranéen
Erpicum, Michel; Binard, Marc

in Notes de Recherches de la Société Géographique de Liège (1988), 10

Les potentialités climatiques des régions touristiques dépendent des impressions de confort ou d'inconfort climatique ressenties par les candidats touristes. Ces impressions dépendent de l'état du ciel, de sa luminosité, du rayonnement solaire, du vent, de la température et de l'humidité de l'air. Une journée à ciel bouché et sombre a tendance à inhiber l'entrain des touristes. Le vent peut être vivement souhaité lors de fortes canicules alors, qu'à même vitesse, il pourrait causer des désagréments évidents par temps très humide ou froi. Ni la pluie, ni aucun extrême climatique n'enchantent le touriste. Par contre, un vent inférieur à 20 km/h, un bon ensoleillement, une humidité relative de l'air comprise entre 65 et 80 % ou une couverture neigeuse skiable constituent des potentialités certaines pour la pratique d'activités touristiques. Les sensations de confort ou d'inconfort climatique sont toujours associées à des combinaisons plus ou moins complexes des éléments du climat vécu. Les potentialités climatiques des types de temps successifs dépendent aussi des potentialités touristiques des régions concernées: type de patrimoine culturel disponible (de plein air ou non), proximité de la mer ou de larges étendues d'eau, existence d'espaces naturels et de paysages variés, etc. Leur évaluation est très difficile à établir et cela même pour le domaine méditerranéen qui est loin d'être homogène, étant donné sa grande diversité orographique et son étendue : 3 700 km de Gibraltar, à Beyrouth et 1 400 km de Trieste à Tripoli.

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See detailCaractérisation des types de temps ou ambiances climatiques à l'échelle locale ou régionale : Proposition d'une méthode de travail
Erpicum, Michel; Alexandre, Jean

in Publications de l'Association Internationale de Climatologie (1988), 1

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See detailClimatology, Fluvial Hydrology and Tropical Geomorphology at the University of Liège
Alexandre, Jean; Erpicum, Michel; Petit, François; Soyer, J.

in Bulletin de la Société Belge d'Études Géographiques (1988), 57(1), 91-107

See detailClimatologie : analyse des nuages vus de l'espace
Erpicum, Michel

in Wilmet, Jules (Ed.) Télédétection satellitaire (1987)

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See detailVariation de la température des eaux de source et de leurs débits en fonction de leur mode d'alimentation. Exemples pris en Lorraine belge
Petit, François; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1987), 22-23

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See detailClimat et paysage : la visibilité, élément méconnu du climat
Erpicum, Michel; Binard, M.

in Notes de Recherches de la Société Géographique de Liège (1987), 8

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See detailUne méthode d'analyse des caractéristiques de la saison des pluies en région sahélienne (exemples pris au Sénégal)
Erpicum, Michel; Binard, Marc; Peters, J.-P.; Alexandre, Jean

in Erpicum, Michel (Ed.) Actes des journées de climatologie (1987)

Starting from the daily data supplied by four stations Saint-Louis. Dakar, Tambacounda and Ziguinchor, a method of characterization of the rainy season in the Sahelian region is proposed. It is founded on: a) the computation of ten-day amounts of precipitation moving from day to day and being greater than 30 mm; b) the computation of percentages of rainy days and percentages of dry days included in dry spells of 1 to 3, 4 to 7. 8 to 14, 15 to 30 and more than 30 days duration. These percentages are computed for every five-days period (6 per month) of the part of the year during which it can rain. These percentages are computed from forty successive years (1939 - 1978).

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See detailSurveillance des variations de la nappe d'eau superficielle en Fagne de Duret (Deux Séries) et du Setay
Streel, Maurice; Erpicum, Michel; Groulard, J. M.; Crahay, M.

in Hautes Fagnes (1987), 188

See detailActes du Colloque International sur la Topoclimatologie et ses applications
Erpicum, Michel

Book published by UGI - Presses Universitaires de Liège (1985)

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See detailVariations de la nappe d'eau superficielle en relation avec le colmatage des drains en Fagne des Deux Séries
Streel, Maurice; Erpicum, Michel; Groulard, J. M.; Crahay, M.

in Hautes Fagnes (1985), 180

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See detailVariabilité spatiale et possibilité d'extrapolation des extrêmes quotidiens de la température dans une région à relief accidenté. Le cas du sud-est de la Belgique
Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1984), 20

See detailEvolution diurne des profils thermiques inversifs les plus courants observés le long de la tour du Bol d'Air au SSW de Liège
Grilli-Delrez, A.; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1984), 20

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See detailAnalyse et interprétation des contrastes thermiques "plateau - vallée" en Haute-Belgique en fonction de la situation atmosphérique générale et de la connaissance de paramètres climatiques du rayonnement et de la stabilité de l'air
Erpicum, Michel

in ZESZYTY NAUKOWE UNIWERSYTETU JAGIELLOŃSKIEGO PRACE GEOGRAFICZNE (1983), 57

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See detailEvaluation de l'évapotranspiration réelle d'une pessière. Comparaison avec l'évapotranspiration potentielle
Petit, François; Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1983), 19

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See detailVariabilité intra- et interannuelle des extrêmes journaliers de la température: proposition d'une méthode de travail.
Erpicum, Michel; Alexandre, Jean

in Hommes et Terres du Nord (1983), 1983-3

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See detailLes contrastes thermiques nocturnes entre vallée et plateau : esquisse de leur modélisation à partir de facteurs climatiques locaux et régionaux mesurés en Haute-Belgique
Erpicum, Michel

in Recherches Géographiques à Strasbourg (1980), 13-14

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See detailLes grandes lignes de l'élaboration des prévisions météorologiques à brève échéance
Erpicum, Michel; Ocula, R.

in G.E.O. (1980), 7

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See detailLe climat de vallée en Haute-Belgique : Analyse en fonction des types de temps
Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1979), 15

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See detailVariabilité de la répartition spatiale des précipitations sur l'agglomération de Liège. Analyse de quelques cas
Erpicum, Michel

in Bulletin de la Société Géographique de Liège (1977), 13(mars 1977), 133-145