Publications of Maxime Prignon
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See detailQuantification of Stratospheric Ozone Recovery Due to Anthropogenic Halogens
Salawitch, R. J.; Tribett, W.; Wales, P. et al

Conference (2020, January 14)

Human release of CFCs and other ozone depleting substances (ODS) has led to a slow, steady erosion of the thickness of the global ozone layer over the past several decades. The ozone layer has begun to ... [more ▼]

Human release of CFCs and other ozone depleting substances (ODS) has led to a slow, steady erosion of the thickness of the global ozone layer over the past several decades. The ozone layer has begun to recover due to actions taken under the Montreal Protocol, which has led to a decrease in the atmospheric abundance of ozone depleting substances. Yet, unreported emissions of CFC-11 have led to a slower than expected decline, and there has been a rise in the atmospheric abundance of chlorinated very short lived (VSL) compounds not regulated under the Montreal Protocol. In this presentation, we examine time series of ozone and halogens from a variety of observational platforms to quantify the attribution of the change in stratospheric ozone that is due to halogens. Our focus is on the extra-polar region: i.e., the state of the ozone layer between 55S and 55N where the vast majority of the world’s population resides. We will quantify the effect of continued release of CFC-11 and the presence of chlorinated VSL species on the recovery of the ozone layer. Additionally, we will use atmospheric observations to evaluate several proposed formulations for defining the quantity known as “Equivalent Effective Stratospheric Chlorine” (EESC) and assess the impact of these formulations on the projected recovery of the ozone layer. [less ▲]

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See detailN2O-based climatology of the Brewer-Dobson Circulation in WACCM, a chemical renalysis and a CTM driven by four dynamical reanalyses
Minganti, Daniele ULiege; Chabrillat, Simon; Christophe, Yves et al

Poster (2019, December 11)

The Brewer-Dobson Circulation (BDC) plays a major role in the stratospheric dynamics in terms of tracer transport through the mean residual meridional advection and the isentropic two-way mixing. The ... [more ▼]

The Brewer-Dobson Circulation (BDC) plays a major role in the stratospheric dynamics in terms of tracer transport through the mean residual meridional advection and the isentropic two-way mixing. The climatological BDC in the Whole Atmosphere Community Climate Model (WACCM) is separated in those components and evaluated through a comparison with a chemical reanalysis of Aura MLS (BRAM2) and with a chemistry-transport model driven by four modern reanalyses (ERA-Interim, JRA-55, MERRA and MERRA2), using the Transformed Eulerian Mean (TEM) analysis of the long-lived tracer N2O and focusing on the vertical residual advection and the horizontal two-way mixing terms. In the wintertime Southern polar region the horizontal mixing term in WACCM shows near-zero values, while all the reanalyses show strong negative contributions. This disagreement is likely due to the different representation of the polar transport barrier, that affects the mixing inside the polar vortex. In this region the reanalyses are characterized by large uncertainties of the TEM analysis, i.e. the residual term of the budget is quite large (the N2O TEM budget is not fully closed). In the wintertime Northern polar latitudes WACCM shows smaller values of the horizontal mixing term compared to the reanalyses, which show lower uncertainties of the TEM budget. The agreement is improved in the middle and low latitudes, especially in the Northern Hemisphere: the differences are smaller and the residual term is lower compared to the polar latitudes. The inter-annual variability of the horizontal mixing term is large in the Southern polar latitudes during austral fall and in the Northern polar latitudes during boreal winter. [less ▲]

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See detailSurveillance à long terme de l’atmosphère terrestre à la station du Jungfraujoch
Mahieu, Emmanuel ULiege; Flock, Olivier ULiege; Notholt, Justus et al

in Bulletin de la Société Royale des Sciences de Liège (2019, November), 88

It is in the early 1950s that researchers from the University of Liège have recorded the first atmospheric solar spectra at the Jungfraujoch scientific station, in the Swiss Alps, at a time when climate ... [more ▼]

It is in the early 1950s that researchers from the University of Liège have recorded the first atmospheric solar spectra at the Jungfraujoch scientific station, in the Swiss Alps, at a time when climate change was not a matter of worry. These pioneering observations have allowed to confirm that methane and carbon monoxide were ubiquitous constituents of the Earth’s atmosphere. The recording of atmospheric spectra resumed in the mid-1970s, stimulated by rising concerns related to possible stratospheric ozone depletion. Since then, this monitoring activity has been conducted at that site without interruption, allowing to gather high-quality data crucial for the characterization of the Earth’s atmosphere and of the changes affecting it, resulting from anthropogenic activities or natural causes. In this paper, we present some recent results relevant for the verification of international environmental treaties. [less ▲]

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See detailImproved FTIR retrieval strategy for HCFC-22 (CHClF2), comparisons with in situ and satellite datasets with the support of models, and determination of its long-term trend above Jungfraujoch
Prignon, Maxime ULiege; Chabrillat, Simon; Minganti, Daniele ULiege et al

in Atmospheric Chemistry and Physics (2019), 19(19), 1230912324

Hydrochlorofluorocarbons (HCFCs) are the first, but temporary, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs). In this work, we present and validate an improved method to ... [more ▼]

Hydrochlorofluorocarbons (HCFCs) are the first, but temporary, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs). In this work, we present and validate an improved method to retrieve the most abundant HCFC in the atmosphere, allowing its evolution to be monitored independently in the troposphere and stratosphere. These kinds of contributions are fundamental for scrutinizing the fulfilment of the Montreal Protocol on Substances that Deplete the Ozone Layer. [less ▲]

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See detailPost-peak trend of upper stratospheric hydrogen chloride derived from ground-based FTIR solar spectra and model simulations
Mahieu, Emmanuel ULiege; Prignon, Maxime ULiege; Servais, Christian ULiege et al

Conference (2019, May 23)

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented ... [more ▼]

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented, characterized by short-term variability which was attributed to atmospheric circulation changes, affecting mainly the lower stratosphere (Mahieu et al., 2014). This notably led to a temporary increase of HCl over 2007-2011, complicating the determination of the long-term HCl trend and the accurate verification of the success of the Montreal Protocol for the protection of the stratospheric ozone layer. Studies have used other long-lived tracers to remove the effects of dynamical variability in the lower stratosphere (e.g., Stolarski et al., 2018), while other investigations have suggested that trends in the upper stratosphere were potentially more appropriate for the long-term characterization of the HCl decrease (e.g., Froidevaux et al., 2015; Bernath and Fernando, 2018), especially when dealing with satellite height-resolved data. In this contribution, we use FTIR (Fourier Transform InfraRed) data from the Jungfraujoch station (Swiss Alps, 3580 m a.s.l.), a site of the NDACC network (http://www.ndacc.org), to study the evolution of HCl in some detail. The SFIT-4 retrieval algorithm implementing the Optimal Estimation Method of Rodgers (2000) is employed, providing HCl columns with good sensitivity from the tropopause up to about 40 km altitude. Moreover, the vertical resolution is sufficient to determine independent partial columns for the lower and upper stratosphere. With the support of model simulations performed with the 3D-Chemistry Transport Model of the Belgian Assimilation System for Chemical ObsErvations (BASCOE; Chabrillat et al., 2018), driven by the ERA-Interim meteorological reanalysis, we investigate the post-peak trend of HCl in the lower and upper stratosphere. We also determine the magnitude of the uncertainties affecting the various trends, using bootstrap tools which are specifically developed to take into account the auto-correlation present in our geophysical data sets. [less ▲]

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See detailInvestigation of stratospheric circulation using long-lived tracers with WACCM, BASCOE CTM and a reanalysis of MLS observations
Minganti, Daniele ULiege; Chabrillat, Simon; Christophe, Yves et al

Poster (2019, April 12)

The stratospheric circulation is investigated using WACCM4 (Whole Atmosphere Community Climate Model version 4), together with BASCOE CTM (Belgian Assimilation System for Chemical Observations Chemistry ... [more ▼]

The stratospheric circulation is investigated using WACCM4 (Whole Atmosphere Community Climate Model version 4), together with BASCOE CTM (Belgian Assimilation System for Chemical Observations Chemistry-Transport Model) and a reanalysis of stratospheric composition observed by MLS: BRAM2 (BASCOE Reanalysis of AURA MLS release 2) over the period 2005-2015. Three different reanalyses of the wind fields (ERA-interim, JRA55 and MERRA2) are used to drive the CTM, providing an estimate of the uncertainties in our representation of the actual stratospheric circulation. We use a long-lived tracer (N2O), and the Transformed Eulerian Mean (TEM) framework to analyse the tracer budget. We focus on the residual advection (mainly vertical) and eddy mixing (mainly horizontal) contributions to the N2O variations, studying the mean annual cycle and variability in the higher stratosphere and how it is depicted in the different datasets. The BRAM2 mean annual cycle, for both the vertical and the horizontal terms, is nearly in the middle of the spread. WACCM is in good agreement concerning the vertical term but differs considerably from the other datasets in the horizontal (~mixing) term. WACCM present a smaller variability with respect to the reanalysis in the Tropical higher stratosphere, especially for the vertical term. The next step of our research is to perform such analysis with the newer version of WACCM (version 6) as well as new BASCOE CTM runs using other reanalysis products. Multi-decadal changes in the terms of the budget, and their space dependence, will be investigated as well. [less ▲]

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See detailImpact of lower stratospheric dynamical variability on total inorganic fluorine derived from ground-based FTIR, satellite and model data
Prignon, Maxime ULiege; Bernath, P. F.; Chabrillat, S. et al

Poster (2019, April 12)

Long-lived tracer concentrations in the lower stratosphere are affected by short time scale circulation variability as highlighted by recent papers (e.g., Mahieu et al., 2014). Many tracers, such as ... [more ▼]

Long-lived tracer concentrations in the lower stratosphere are affected by short time scale circulation variability as highlighted by recent papers (e.g., Mahieu et al., 2014). Many tracers, such as hydrogen chloride (HCl) or hydrogen fluoride (HF) have now been successfully used to investigate or identify this variability (e.g., Harrison et al., 2016) In this work, the main reservoirs of inorganic fluorine [i.e., HF, carbonyl fluoride (COF2) and carbonyl chloride fluoride (COClF)] and their sum (total inorganic fluorine, Fy) are used to investigate the lower stratospheric circulation changes. We use Fourier Transform InfraRed (FTIR) ground-based observations conducted in the framework of the NDACC network (http://www.ndacc.org) to derive column abundances of HF and COF2, thus providing a good proxy for Fy. To support this research, we also include satellite observations from HALOE (HF available) and ACE-FTS (HF, COF2 and COClF available). Moreover, we use the Chemical-Transport Model (CTM) BASCOE (Belgian Assimilation System for Chemical ObsErvations; Chabrillat et al., 2018) to evaluate the representation of the investigated circulation changes in state-of-the-art meteorological reanalyses. We also evaluate if WACCM4 (Whole Atmosphere Community Climate Model version 4) is able to reproduce these changes through a free dynamics and free chemistry run. Finally, SLIMCAT CTM (Chipperfield et al., 2015) simulations are included to provide information on the partitioning between the main Fy reservoirs. [less ▲]

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See detailPOst-peak trend of upper stratospheric hydrogen chloride derived from ground-based FTIR solar spectra and model simulations
Mahieu, Emmanuel ULiege; Prignon, Maxime ULiege; Servais, Christian ULiege et al

Conference (2019, April 12)

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented ... [more ▼]

After several decades of sustained increase, hydrogen chloride (HCl, the main reservoir for stratospheric chlorine) showed a maximum abundance around 1997. Since then, its decrease has been documented, characterized by short-term variability which was attributed to atmospheric circulation changes, affecting mainly the lower stratosphere (Mahieu et al., 2014). This notably led to a temporary increase of HCl over 2007-2011, complicating the determination of the long-term HCl trend and the accurate verification of the success of the Montreal Protocol for the protection of the stratospheric ozone layer. Studies have used other long-lived tracers to remove the effects of dynamical variability in the lower stratosphere (e.g., Stolarski et al., 2018), while other investigations have suggested that trends in the upper stratosphere were potentially more appropriate for the long-term characterization of the HCl decrease (e.g., Froidevaux et al., 2015; Bernath and Fernando, 2018), especially when dealing with satellite height-resolved data. In this contribution, we use FTIR (Fourier Transform InfraRed) data from the Jungfraujoch station (Swiss Alps, 3580 m a.s.l.), a site of the NDACC network (http://www.ndacc.org), to study the evolution of HCl in some detail. The SFIT-4 retrieval algorithm implementing the Optimal Estimation Method of Rodgers (2000) is employed, providing HCl columns with good sensitivity from the tropopause up to about 40 km altitude. Moreover, the vertical resolution is sufficient to determine independent partial columns for the lower and upper stratosphere. With the support of model simulations performed with the 3D-Chemistry Transport Model of the Belgian Assimilation System for Chemical ObsErvations (BASCOE; Chabrillat et al., 2018), driven by the ERA-Interim meteorological reanalysis, we investigate the post-peak trend of HCl in the lower and upper stratosphere. We also determine the magnitude of the uncertainties affecting the various trends, using bootstrap tools which are specifically developed to take into account the auto-correlation present in our geophysical data sets. [less ▲]

Detailed reference viewed: 36 (3 ULiège)
See detailAnalysis of trends in total stratospheric ozone
Salawitch, Ross J; Tribett, W R; Wales, P et al

Conference (2018, December 12)

Time series of total column ozone have exhibited unusual, unexpected behavior over the past few years. In year 2016, total ozone was lower than expected based on some forecasts that utilize the time ... [more ▼]

Time series of total column ozone have exhibited unusual, unexpected behavior over the past few years. In year 2016, total ozone was lower than expected based on some forecasts that utilize the time evolution of equivalent effective stratosphere chlorine (EESC). Conversely, total column ozone exhibited a sharp rise in 2017. The existence of a new formulation (i.e., Engel et al., ACP, 2017) for the fractional release factors (FRFs) used to find EESC for mid-latitude lower stratospheric air parcels, the contribution of very short-lived chlorine and bromine compounds to EESC, as well as possible temporal variations in tropospheric column ozone compound the difficulty in establishing a quantitative relationship between the time evolution of EESC and stratospheric ozone. This presentation will consist of an analysis of the ~40 year record of total column ozone measured from space (e.g., version 8.6 of the NASA SBUV Merged Ozone Data Set at the time of abstract submission), along with: a) stratospheric chlorine loading from various satellite instruments as well as the long-term ground-based measurement from Jungfraujoch, Switzerland; b) various other quantities that affect the long-term evolution of stratospheric ozone (e.g., total solar irradiance, stratospheric optical depth, quasi-biennial oscillation of the direction of tropical stratospheric winds) c) estimates of tropospheric column ozone to assess our understanding of trends in total stratospheric ozone. Preliminary results indicate better quantitative understanding is attained for the new FRFs, which lead to a more gradual recovery of total stratospheric ozone than is found using the old FRFs. Reference: Engel, A. et al., ACP, 18, 601619, doi:10.5194/acp-18-601-2018, 2018. [less ▲]

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See detailUpdate on the FTIR monitoring program at the Jungfraujoch station
Mahieu, Emmanuel ULiege; Prignon, Maxime ULiege; Servais, Christian ULiege

Scientific conference (2018, October 31)

We present a report on the status of the FTIR monitoring program at the Jungfraujoch station. Focus is put on the reanalysis of the HCFC-22 (CHClF2) time series and to our first attempt to retrieve PAN ... [more ▼]

We present a report on the status of the FTIR monitoring program at the Jungfraujoch station. Focus is put on the reanalysis of the HCFC-22 (CHClF2) time series and to our first attempt to retrieve PAN from ground-based infrared solar absorption spectra. Ongoing investigations regarding two heavy stable isotopologues of methane (13CH4 and CH3D) are also presented. [less ▲]

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See detailObservation and simulation of ethane (C2H6) at 23 FTIR sites
Mahieu, Emmanuel ULiege; Franco, B.; Pozzer, A. et al

in Geophysical Research Abstracts (2018, April 11), 20

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See detailAttempting to retrieve peroxyacetyl nitrate from ground-based infrared solar spectra
Mahieu, Emmanuel ULiege; Fischer, Emily V.; Tzompa-Sosa, Zitely A. et al

in Geophysical Research Abstracts (2018, April 09), 20

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See detailACCROSS Project: Investigating the impacts of circulation changes on stratospheric tracers
Prignon, Maxime ULiege; Chabrillat, Simon; Mahieu, Emmanuel ULiege

Poster (2018, January 12)

The ACCROSS project (Atmospheric Composition and Circulation investigated with meteorological Reanalyses, Observational datasets and models for the Study of the Stratosphere and its changes) aims to ... [more ▼]

The ACCROSS project (Atmospheric Composition and Circulation investigated with meteorological Reanalyses, Observational datasets and models for the Study of the Stratosphere and its changes) aims to improve our understanding of the circulation changes in the stratosphere during the past three decades. To achieve this objective, miscellaneous observational datasets and model simulations are used. Here are presented the main aspects and the first preliminary results of the project. In the framework of the recent studies demonstrating the influence of stratospheric circulation changes on the trend of long-lived tracers (e.g. hydrogen chlorine), we decided to investigate the impact of these circulation changes on hydrogen fluoride (HF). Fourier-Transform infrared spectroscopy data produced at the Jungfraujoch NDACC site and satellite data (HALOE and ACE) are used to evaluate the HF trends. Moreover, to support our data interpretation, chemistry-transport model BASCOE simulations are also included. These early investigations show a modulation in HF time series at Jungfraujoch occurring around 2007. At the time being, it seems that BASCOE driven by ERA-Interim reanalysis cannot capture this modulation. [less ▲]

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See detailObservation and simulation of ethane (C2H6) at 23 FTIR sites
Mahieu, Emmanuel ULiege; Franco, B; Pozzer, A et al

Poster (2017, December 13)

Ethane is the most abundant non-methane hydrocarbon (NMHC) in the Earth atmosphere. Its main sources are of anthropogenic origin, with globally 62% from leakage during production and transport of natural ... [more ▼]

Ethane is the most abundant non-methane hydrocarbon (NMHC) in the Earth atmosphere. Its main sources are of anthropogenic origin, with globally 62% from leakage during production and transport of natural gas, 20% from biofuel combustion and 18% from biomass burning. In the Southern hemisphere, anthropogenic emissions are lower which makes biomass burning emissions a more significant source. The main removal process is oxidation by the hydroxyl radical (OH), leading to a mean atmospheric lifetime of 2 months. Until recently, a prolonged decrease of its abundance has been documented, at rates of -1 to -2.7%/yr, with global emissions dropping from 14 to 11 Tg/yr over 1984-2010 owing to successful measures reducing fugitive emissions from its fossil fuel sources. However, subsequent investigations have reported on an upturn in the ethane trend, characterized by a sharp rise from about 2009 onwards. The ethane increase is attributed to the oil and natural gas production boom in North America, although significant changes in OH could also be at play.In the present contribution, we report the trend of ethane at 23 ground-based Fourier Transform Infrared (FTIR) sites spanning the 80ºN to 79ºS latitude range. Over 2010-2015, a significant ethane rise of 3-5%/yr is determined for most sites in the Northern Hemisphere, while for the Southern hemisphere the rates of changes are not significant at the 2-sigma uncertainty level. Dedicated model simulations by EMAC (ECHAM5/MESSy Atmospheric Chemistry; ~1.8×1.8 degrees) implementing various emission scenarios are included in order to support data interpretation. The usual underestimation of the NMHCs emissions in the main inventories is confirmed here for RCP85 (Representative Concentration Pathway Database v8.5). Scaling them by 1.5 is needed to capture the background levels of atmospheric ethane. Moreover, additional and significant emissions (~7 Tg over 2009-2015) are needed to capture the ethane rise in the Northern hemisphere. Attributing them to the oil and gas sector and locating them in North America allows EMAC to produce adequate trends in the Northern hemisphere, but not in the Southern hemisphere, where they are overestimated. Possible causes for this difference are discussed. [less ▲]

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See detailSurveillance de l'atmosphère terrestre depuis la station du Jungfraujoch : une épopée liégeoise entamée voici plus de 65 ans !
Mahieu, Emmanuel ULiege; Bader, Whitney ULiege; Bovy, Benoît ULiege et al

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

It’s in the early 1950s that researchers from the University of Liège started to investigate the Earth’s atmosphere from the Jungfraujoch scientific station, in the Swiss Alps, at a time when concerns ... [more ▼]

It’s in the early 1950s that researchers from the University of Liège started to investigate the Earth’s atmosphere from the Jungfraujoch scientific station, in the Swiss Alps, at a time when concerns related to atmospheric composition changes were nonexistent. Since then, an infrared observational data base unique worldwide has been carefully collected. The exploitation of these observations has allowed constituting multi-decadal time series crucial for the characterization of the changes that affected our atmosphere and for the identification of their causes. In this paper, we first remind about the successive steps which led to establishing the observational program of the Liège team at the Jungfraujoch and we evoke important findings which justified its continuation. Then we present some recent results relevant to the Montreal and Kyoto Protocols, or related to the monitoring of air quality. [less ▲]

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See detailObservation and simulation of ethane at 22 FTIR sites
Mahieu, Emmanuel ULiege; Franco, Bruno ULiege; Pozzer, Andrea et al

Conference (2017, May 30)

Detailed reference viewed: 78 (8 ULiège)