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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 detailSensitivity of the current Antarctic surface mass balance to sea surface conditions using MAR
Kittel, Christoph; Amory, Charles; Agosta, Cécile; Delhasse, Alison; Doutreloup, Sébastien; Huot, Pierre-Vincent; Wyard, Coraline; Fichefet, Thierry; Fettweis, Xavier

in Cryosphere (2018), 12

Estimates for the recent period and projections of the Antarctic surface mass balance (SMB) often rely on high-resolution polar-oriented regional climate models (RCMs). However, RCMs require large-scale boundary forcing fields prescribed by reanalyses or general circulation models (GCMs). Since the recent variability of sea surface conditions (SSCs, namely sea ice concentration, SIC, and sea surface temperature, SST) over the Southern Ocean is not reproduced by most GCMs from the 5th phase of the Coupled Model Intercomparison Project (CMIP5), RCMs are then subject to potential biases. We investigate here the direct sensitivity of the Antarctic SMB to SSC perturbations around the Antarctic. With the RCM “Modèle Atmosphérique Régional” (MAR), different sensitivity experiments are performed over 1979–2015 by modifying the ERA-Interim SSCs with (i) homogeneous perturbations and (ii) mean anomalies estimated from all CMIP5 models and two extreme ones, while atmospheric lateral boundary conditions remained unchanged. Results show increased (decreased) precipitation due to perturbations inducing warmer, i.e. higher SST and lower SIC (colder, i.e. lower SST and higher SIC), SSCs than ERA-Interim, significantly affecting the SMB of coastal areas, as precipitation is mainly related to cyclones that do not penetrate far into the continent. At the continental scale, significant SMB anomalies (i.e greater than the interannual variability) are found for the largest combined SST/SIC perturbations. This is notably due to moisture anomalies above the ocean, reaching sufficiently high atmospheric levels to influence accumulation rates further inland. Sensitivity experiments with warmer SSCs based on the CMIP5 biases reveal integrated SMB anomalies (+5 % to +13 %) over the present climate (1979–2015) in the lower range of the SMB increase projected for the end of the 21st century.

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See detailThe CORDEX.be initiative as a foundation for climate services in Belgium
Termonia, P.; Van Schaeybroeck, B.; De Cruz, L.; De Troch, R.; Caluwaerts, S.; Giot, O.; Hamdi, R.; Vannitsem, S.; Duchêne, F.; Willems, P.; Tabari, H.; Van Uytven, E.; Hosseinzadehtalaei, P.; Van Lipzig, N.; Wouters, H.; Vanden Broucke, S.; van Ypersele, J.-P.; Marbaix, P.; Villaunueva-Birriel, C.; Fettweis, Xavier; Wyard, Coraline; Scholzen, C.; Doutreloup, Sébastien; De Ridder, K.; Gobbin, A.; Lauwaet, D.; Stavrakou, T.; Bauwens, M.; Müller, J.-F.; Luyten, P.; Ponsar, S.; Van den Eynde, D.; Pottiaux, E.

in Climate Services (2018), 11

The CORDEX.be project created the foundations for Belgian climate services by producing high-resolution Belgian climate information that (a) incorporates the expertise of the different Belgian climate modeling groups and that (b) is consistent with the outcomes of the international CORDEX (“COordinated Regional Climate Downscaling Experiment”) project. The key practical tasks for the project were the coordination of activities among different Belgian climate groups, fostering the links to specific international initiatives and the creation of a stakeholder dialogue. Scientifically, the CORDEX.be project contributed to the EURO-CORDEX project, created a small ensemble of High-Resolution (H-Res) future projections over Belgium at convection-permitting resolutions and coupled these to seven Local Impact Models. Several impact studies have been carried out. The project also addressed some aspects of climate change uncertainties. The interactions and feedback from the stakeholder dialogue led to different practical applications at the Belgian national level

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See detailGlobal Radiative Flux and Cloudiness Variability for the Period 1959–2010 in Belgium: A Comparison between Reanalyses and the Regional Climate Model MAR
Wyard, Coraline; Doutreloup, Sébastien; Belleflamme, Alexandre; Wild, Martin; Fettweis, Xavier

in Atmosphere (2018), 9(7), 262

The use of regional climate models (RCMs) can partly reduce the biases in global radiative flux (Eg↓) that are found in reanalysis products and global models, as they allow for a finer spatial resolution and a finer parametrisation of surface and atmospheric processes. In this study, we assess the ability of the MAR («Modèle Atmosphérique Régional») RCM to reproduce observed changes in Eg↓, and we investigate the added value of MAR with respect to reanalyses. Simulations were performed at a horizontal resolution of 5 km for the period 1959–2010 by forcing MAR with different reanalysis products: ERA40/ERA-interim, NCEP/NCAR-v1, ERA-20C, and 20CRV2C. Measurements of Eg↓ from the Global Energy Balance Archive (GEBA) and from the Royal Meteorological Institute of Belgium (RMIB), as well as cloud cover observations from Belgocontrol and RMIB, were used for the evaluation of the MAR model and the forcing reanalyses. Results show that MAR enables largely reducing the mean biases that are present in the reanalyses. The trend analysis shows that only MAR forced by ERA40/ERA-interim shows historical trends, which is probably because ERA40/ERA-interim has a better horizontal resolution and assimilates more observations than the other reanalyses that are used in this study. The results suggest that the solar brightening observed since the 1980s in Belgium has mainly been due to decreasing cloud cover.

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See detailAssessing the future evolution of climate extremes favouring floods using the regional climate model MAR over the CORDEX.be domain
Wyard, Coraline; Doutreloup, Sébastien; Fettweis, Xavier

Poster (2018, April 13)

In Belgium, most flooding events occur in winter as a result of intense precipitation events but also to the abrupt melting of the snow that covers the Ardennes summits. These conditions favourable to floods exhibit a decreasing trend over the period 1959–2010 resulting from the reduction in snow accumulation thought extreme precipitation events show a positive but non-significant signal. In this study, we investigate how these trends could evolve in a warmer climate by using future projections performed with the regional climate model MAR (for “Modèle Atmosphérique Régional”) in the framework of CORDEX.be, the Belgian EURO-CORDEX project. These future projections were obtained by nesting MAR into NorESM1-M and MIROC5 under the RCP8.5 scenario. Both these global models were selected from the CMIP5 archive after evaluation of their ability to represent the current (1976-2005) mean climate over Europe. This assessment is based on the skill score methodology. Results show that the period 2071-2100 would be marked by a decrease in snowfall amount, in snow accumulation, and consequently in conditions favourable to floods generated by snowpack melting with respect to 1976-2005. Regarding total PPN amount and extremes, the signal is less clear as both GCMs simulate different patterns and trends.

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See detailCombining regional downscaling expertise in Belgium: CORDEX and beyond
Termonia, Piet; Van Schaeybroeck, Bert; De Cruz, Lesley; De Troch, Rozemien; Giot, Olivier; Hamdi, Rafiq; Vannitsem, Stéphane; Duchêne, François; Willems, Patrick; Tabari, Hossein; Van Uytven, Els; Hosseinzadehtalaei, Parisa; Van Lipzig, Nicole; Wouters, Hendrik; Vanden Broucke, Sam; Demuzere, Matthias; van Ypersele, Jean-Pascal; Marbaix, Philippe; Villanueva-Birriel, Cecille; Fettweis, Xavier; Wyard, Coraline; Scholzen, Chloé; Doutreloup, Sébastien; De Ridder, Koen; Lauwaet, Dirk; Gobin, Anne; Stavrakou, Trissevgeni; Bauwens, Maite; Müller, Jean-François; Luyten, Patrick; Ponsar, Stéphanie; Van den Eynde, Dries; Pottiaux, Eric

Report (2018)

The main objectives of the CORDEX.be project were: 1. Contribute to the international climate community by participating to EURO-CORDEX by performing regional climate simulations over Europe. 2. Provide an ensemble of High-Resolution (H-Res) climate simulations over Belgium i.e. to create a small ensemble of high-resolution future projections over Belgium at convectionpermitting resolutions. 3. Couple these model simulations to seven local-impact models for impact studies. 4. Present an overview of the ongoing climate modeling activities in Belgium. 5. Provide coherent climate information for Belgium targeted to end-users, backed by: (i) a unified framework for the H-Res climate runs and (ii) uncertainty estimations on the climate change signal; 6. Provide and present a climate-impact report for stakeholders and the general public that highlight the most important results of the project.

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See detailWinter season changes in Belgium: the MAR model contribution to the CORDEX.be project
Wyard, Coraline; Doutreloup, Sébastien; Scholzen, Chloé; Fettweis, Xavier

Conference (2017, November 17)

In the framework of the CORDEX.be project funded by Belspo, most universities and research institutes of Belgium have worked together in order to gather existing and ongoing Belgian research activities in the domain of climate modelling to create a coherent scientific basis for future climate services in Belgium. The Laboratory of Climatology of the University of Liège has performed climate simulations using the regional climate model MAR (“Modèle Atmosphérique Régional” in French) at a resolution of 5 km over the period 1959-2014. This research aims to study the evolution of several variables computed by MAR during the winters of the last 50 years. Except in snow accumulation, results show no statistically significant trend in winter temperature or precipitation in Belgium. This results from the strong influence of natural large-scale/low-frequency oscillations in the atmospheric circulation in winter such as the North Atlantic Oscillation.

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See detailThe MAR model : CORDEX.be and EURO-CORDEX results
Wyard, Coraline; Doutreloup, Sébastien; Fettweis, Xavier

Scientific conference (2017, September 14)

This research discusses the results obtained by running the MAR model over the CORDEX.be and EURO-CORDEX domains. The MAR results depend on its horizontal resolution (5 - 10 - 20 km), its version (v3.6 vs v3.7), and on the reanalysis used as forcing.

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See detailSurface solar radiation modelling over 1900-2014: comparison between the regional climate model MAR and reanalyses
Wyard, Coraline; Doutreloup, Sébastien; Belleflamme, Alexandre; Fettweis, Xavier

Poster (2017, September 04)

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 1950s 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 ») which has recently been chosen to be part of the EURO-CORDEX project, thanks to the CORDEX.be project. Simulations were performed at a horizontal resolution of 5 km over a domain of 600 x 550 km² covering Belgium. Boundary conditions were provided by four reanalysis products: ERA-interim (1979-2014) completed by the ERA40 (1958-1978), NCEP/NCAR-v1 (1948-2014), ERA-20C (1900-2010) and 20CRV2C (1900-2010). Surface solar radiation measurements from the Global Energy Balance Archive and cloud cover observations from Belgocontrol covering 1966-2007 were used for the evaluation of the MAR model and the forcing reanalyses. Results show that MAR produces much better results than the reanalyses. The driving reanalyses can generate divergent trends while they assimilate observations and are supposed to represent the same climate.

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See detailNoël 2010 en Belgique : neige en Flandre et pluie en Haute-Ardenne
Fettweis, Xavier; Wyard, Coraline; Doutreloup, Sébastien; Belleflamme, Alexandre

in Bulletin de la Société Géographique de Liège (2017), 68

On December 2010, several snow events allowed an exceptional snow cover over Belgium. 27 days with snow cover were observed at Uccle and snow depths of 20, 30 and 70 cm were measured on Christmas 2010 respectively at Uccle, Bierset and Mont Rigi in the Hautes-Fagnes. On December 20, while the entire Belgium was covered by a thick blanket of snow, warmer air invaded the country on December 21. This air was quickly replaced by polar air in Lower and Central Belgium (including Bierset). Heavy snowfalls were observed on December 22 and 23, except in the Upper Ardennes where rainfalls occurred under positive temperature which then dropped to -5°C. This event was due to a strong thermal inversion in the lower layers with warm air at 850 hPa above the Ardennes only. This paper aims to explain this atypical extreme event using the regional climate model MAR developed at the University of Liège

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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.

See detailModelling past and present distributions of tropical African biomes and species using a dynamic vegetation model.
Dury, Marie; Doutreloup, Sébastien; Hardy, Olivier; Fayolle, Adeline; Fettweis, Xavier; Hambuckers, Alain; Gallee, Hubert; François, Louis

Poster (2017, February 08)

In the framework of the AFRIFORD project (Genetic and paleoecological signatures of African rainforest dynamics: pre-adapted to change?, http://www.ulb.ac.be/facs/sciences/afriford/), we used the CARAIB dynamic vegetation model to simulate past and present distributions of tropical African vegetation at the biome and species levels to better project and understand future dynamics. We studied individual species (e.g., Afzelia africana, Pericopsis elata, etc) for which we determined climatic requirements and gathered specific traits. To perform palaeovegetation reconstructions, we used outputs of snapshot climate simulations (e.g., CNRM-CM5, FGOALS-g2 and MRI-CGCM5 global climatic models) from the PaleoModelling Intercomparison Project (PMIP3, https://pmip3.lsce.ipsl.fr/) for the mid-Holocene (6 ka) and the Last Glacial Maximum (LGM, 21 ka). These global climatic outputs were downscaled at a 0.45° spatial resolution over Equatorial Africa using the MAR regional climate model (RCM). For current conditions, the RCM was nested in different historical climate datasets. We compared modelled species distributions with species occurrences from different databases for present and with palaeorecords for past periods. MAR regional climate simulations notably allow CARAIB to reproduce the Dahomey Gap separating the Upper and Lower Guinean forests in West Africa in present biome distribution. The vegetation model also simulates LGM rainforest distribution in agreement with hypothetical glacial rainforest refuge areas inferred from palaeorecords.

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See detailLes changements climatiques : Causes, conséquences et actions possibles
Doutreloup, Sébastien; Wyard, Coraline; Belleflamme, Alexandre; Merenne-Schoumaker, Bernadette

Book published by FEGEPRO (Fédération des professeurs de géographie) (2017)

Dans une première partie de l’ouvrage, les auteurs traitent de l’état de la question des variations climatiques, en s’attachant aux explications naturelles et anthropiques des variations passées, tout en s’attardant sur les variations du Pléistocène à aujourd’hui. La question des variations attendues pour le futur retient l’attention, présentée sous la forme de différents scénarios, avec un focus porté sur l’Europe. Dans une seconde partie de l’ouvrage, sont abordées les conséquences et impacts spatiaux des variations climatiques. Si la fonte des banquises ainsi que la hausse du niveau des mers ainsi que leur acidification ont retenu l’attention des auteurs, ils s’attardent également sur la multiplication des événements climatiques extrêmes, les changements des écosystèmes, les problématiques des déplacés climatiques et des impacts sanitaires, tout en pointant ce qui reste en débat. La troisième partie consacrée aux politiques et aux actions ne manquera pas de susciter notre curiosité, tant au niveau des solutions techniques, que des modes de production ou de consommation, tout en réaffirmant que les choix politiques posés en matière d’aménagement de territoire et d’urbanisme s’avèrent déterminants pour infléchir sur les comportements individuels.

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See detailClimatologie et météorologie : les notions de base
Doutreloup, Sébastien

Book published by FEGEPRO (Fédération des professeurs de géographie) (2016)

L'objectif de cet ouvrage est de fournir, dans un langage simple et accessible, les bases nécessaires à la compréhension générale du fonctionnement de l’atmosphère et à l'analyse des conditions climatiques globales, régionales et locales. Cet ouvrage a été rédigé à destination des professeurs de géographie de l'enseignement secondaire qui désirent parfaire ou actualiser leurs connaissances, des enseignants qui ne disposent pas d'une formation initiale en géographie, ou des étudiants des Hautes-Écoles qui souhaitent disposer d'une synthèse scientifique sur le domaine. Mais cet ouvrage s'adresse également à l'ensemble des lecteurs curieux qui ont envie de découvrir ou redécouvrir la science du climat.

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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 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 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 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 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 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 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 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 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 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 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 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 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 detailInterests of using a regional model to forecast wind power production
Doutreloup, Sébastien

Poster (2010, November 05)

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 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 detailAnalysis of the evolution of the climate parameters, especially precipitations and temperatures, in the province of Binh Thuan in Southern Vietnam based on IPCC models
Doutreloup, Sébastien; Fettweis, Xavier; Ozer, Pierre

Report (2010)

This research is implied into the BELSPO / Vietnamese desertification project and the aim of this work is to analyse the future evolution of the temperatures and precipitations in the region of Binh Thuan thanks to the IPCC models (CMIP3).

See detailAmélioration d’un modèle de prévision quart horaire des productions des parcs éoliens d’Amel et de Perwez en Belgique.
Doutreloup, Sébastien

Master's dissertation (2009)

Une société de distribution d'électricité a sollicité le Laboratoire de Climatologie (ULg) pour lui fournir, tous les jours à 8 heures du matin, la prévisions de la production électrique pour deux parcs éoliens en Belgique, avec un pas de temps de 15 minutes. Depuis janvier 2008, un modèle opérationnel a été élaboré dans ce laboratoire pour calculer ces prévisions. Ce mémoire a contribué à l'amélioration de ce modèle de prévisions de production d'énergie électrique d'origine éolienne. Le modèle opérationnel mis en exploitation à la suite de ce mémoire reste relativement simple et ne fait intervenir que peu de ressources informatiques. En effet, le temps nécessaire pour calculer la prévision est très court car le modèle utilise directement les sorties du modèle global de prévisions météorologique « Global Forecast System » (GFS) sans downscaling, contrairement à ce qui est proposé dans cette thèse. Le but de ce mémoire était donc d'apporter des améliorations au modèle opérationnel et ainsi d'améliorer la qualité des prévisions de production rendues. Afin de créer ces améliorations et de les tester dans de bonnes conditions, nous avons, tout d'abord, trié nos données d'observations et de prévisions afin de nous affranchir des erreurs d'observations et de transmissions de la production des parcs éoliens et des imprécisions liées à l'utilisation de prévisions météorologiques. Les données d'observation sont parfois biaisées dues à l'arrêt des éoliennes, principalement pour cause de givre ou de maintenance. Les prévisions GFS utilisées dans le modèle opérationnel contenaient beaucoup d'erreurs liées à l'utilisation des prévisions météorologiques de la veille (00hTU) pour calculer les prévisions de production pour le lendemain. Pour calculer et mettre à l'épreuve les améliorations apportées au modèle, nous avons utilisé les prévisions de GFS les plus récentes possibles (toutes les 6 heures) de chaque prévision de production, et qui sont donc a priori les meilleures possibles. Une fois libéré de ces contraintes, nous avons alors testé une série d'éléments liés aux sites d'implantation des éoliennes afin d'améliorer les prévisions des productions des deux parcs. Différents éléments d'amélioration ont été retenus : - Une rose des rugosités : Cette amélioration a permis de corriger la vitesse du vent modélisée selon la direction d'où il provenait, suivant la présence d'obstacles de natures diverses (des arbres, une colline, une vallée, ...) - Une modification de la production en fonction de la densité de l'air qui influence la productivité des éoliennes pour une même vitesse de vent. - Un calibrage par rapport à l'indice K-Index qui caractérise l'instabilité de l'atmosphère et donc les rafales de vent dues aux mouvements convectifs locaux qui ne sont pas modélisés par GFS. - Un calibrage par rapport aux amplitudes thermiques diurnes qui influencent les vents locaux non modélisés par GFS. Au final, nous avons pu améliorer les prévisions de l'ordre de 20% pour le premier parc et de l'ordre de 5% pour le second par rapport au modèle de base. La faible amélioration pour le second parc provient du fait que les prévisions étaient déjà de bonne qualité dans le modèle opérationnel originel et que les calibrations empiriques contenues dans ce modèle suffisaient, contrairement contrairement au premier parc dont la physionomie du terrain à proximité des éoliennes était très complexe.