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Formic acid (HCOOH) concentrations are often underestimated by models, and its chemistry is highly uncertain. HCOOH is, however, among the most abundant atmospheric volatile organic compounds, and it is potentially responsible for rain acidity in remote areas. HCOOH data from the Infrared Atmospheric Sounding Interferometer (IASI) are analyzed from 2008 to 2014 to estimate enhancement ratios from biomass burning emissions over seven regions. Fire-affected HCOOH and CO total columns are defined by combining total columns from IASI, geographic location of the fires from Moderate Resolution Imaging Spectroradiometer (MODIS), and the surface wind speed field from the European Centre for Medium-Range Weather Forecasts (ECMWF). Robust correlations are found between these fire-affected HCOOH and CO total columns over the selected biomass burning regions, allowing the calculation of enhancement ratios equal to 7.30g × g 10g'3g ±g 0.08g × g 10g'3g molg molg'1 over Amazonia (AMA), 11.10g × g 10g'3g ±g 1.37g × g 10g'3g molg molg'1 over Australia (AUS), 6.80g × g 10g'3g ±g 0.44g × g 10g'3g molg molg'1 over India (IND), 5.80g × g 10g'3g ±g 0.15g × g 10g'3g molg molg'1 over Southeast Asia (SEA), 4.00g × g 10g'3g ±g 0.19g × g 10g'3g molg molg'1 over northern Africa (NAF), 5.00g × g 10g'3g ±g 0.13g × g 10g'3g molg molg'1 over southern Africa (SAF), and 4.40g × g 10g'3g ±g 0.09g × g 10g'3g molg molg'1 over Siberia (SIB), in a fair agreement with previous studies. In comparison with referenced emission ratios, it is also shown that the selected agricultural burning plumes captured by IASI over India and Southeast Asia correspond to recent plumes where the chemistry or the sink does not occur. An additional classification of the enhancement ratios by type of fuel burned is also provided, showing a diverse origin of the plumes sampled by IASI, especially over Amazonia and Siberia. The variability in the enhancement ratios by biome over the different regions show that the levels of HCOOH and CO do not only depend on the fuel types., SCOPUS: ar.j, info:eu-repo/semantics/published

Atmospheric CO at Egham in SE England has shown a marked and progressive decline since 1997, following adoption of strict controls on emissions. The Egham site is uniquely positioned to allow both assessment and comparison of ‘clean Atlantic background’ air and CO-enriched air downwind from the London conurbation. The decline is strongest (approximately 50 ppb per year) in the 1997–2003 period but continues post 2003. A ‘local CO increment’ can be identified as the residual after subtraction of contemporary background Atlantic CO mixing ratios from measured values at Egham. This increment, which is primarily from regional sources (during anticyclonic or northerly winds) or from the European continent (with easterly air mass origins), has significant seasonality, but overall has declined steadily since 1997. On many days of the year CO measured at Egham is now not far above Atlantic background levels measured at Mace Head (Ireland). The results are consistent with MOPITT satellite observations and ‘bottom-up’ inventory results. Comparison with urban and regional background CO mixing ratios in Hong Kong demonstrates the importance of regional, as opposed to local reduction of CO emission. The Egham record implies that controls on emissions subsequent to legislation have been extremely successful in the UK. ISSN:2045-2322

International audience; With fast economic growth and development China is experiencing severe air pollution episodes related to rapid industrialization and urbanization since more than three decades. Through collaboration between 7 European and 7 Chinese research universities and institutes, the PANDA (Partnership with China on Space Data) EU-funded project aims to improve our understanding of the processes responsible for the formation, dispersion and destruction of air pollutants in East Asia. By combining space and in-situ observations and surface emissions of chemical pollutants with global and regional models of atmospheric composition, detailed analyses and reliable forecasts of regional air quality are produced with the aim of improving methods for monitoring and forecasting air quality in East Asia.Using a multi-model approach based on several global and regional state-of the art model simulations, we present detailed modeling studies of recent notorious haze events in East Asia (winter 2010 and 2013 haze events). We will demonstrate the effect of uncertainties and differences in current emission inventories for China and their resolution and temporal variation on model performance. We will focus especially on major city clusters that have experienced intense urbanization and population growth. The importance of using a downscaling approach to better reproduce and predict air pollution events that occur in East Asia will be discussed. The relation between the performance of the models and the complexity of their chemistry and aerosol schemes and choice of boundary and atmospheric forcing will be assessed. We will also present results of the air quality forecasting system being developed within PANDA and in collaboration with the EU project MarcoPolo.

International audience; Formic acid (HCOOH) is one among the most abundant volatile organic compounds (VOCs) present in the atmosphere. HCOOH sources include emissions from vegetation, soil and biomass burning. To a lesser extent, it is also produced by motor vehicles. It is mainly a secondary product from organic precursors.HCOOH plays a role in the oxidizing capacity of the troposphere and on the global budget of tropospheric ozone (O3), and it is also a source of rain acidity in remote areas. There are however large uncertainties on sources and sinks and HCOOH is misrepresented in the global emissions inventories.In this work, we retrieve concentrations from spectra recorded by the IASI (Infrared Atmospheric Sounding Interferometer) instrument launched onboard the MetOp-A satellite in 2006. IASI is a nadir looking Fourier transform spectrometer, sounding the atmosphere with a global coverage twice per day. The HCOOH global distributions are derived using a new retrieval approach, based on conversion factors between brightness temperature differences and representative retrieved total columns.We present global distributions and comparisons with FTIR measurements obtained at La Reunion, Wollongong and Jungfraujoch from 2008 to 2013. The IASI instrument provides a 6-year record for different regions, highlighting the signatures from biomass burning events and allowing the study of seasonal and interannual variations

International audience; The University of Toronto Atmospheric Observatory and Environment Canada's Centre for Atmospheric Research Experiments each has over a decade of ground-based Fourier transform infrared (FTIR) spectroscopy measurements in southern Ontario. We present the Toronto area FTIR time series from 2002 to 2013 of two tropospheric trace gases—ozone and carbon monoxide—along with surface in situ measurements taken by government monitoring programs. We interpret their variability with the GEOS-Chem chemical transport model and determine the atmospheric conditions that cause pollution events in the time series. Our analysis includes a regionally tagged O3 model of the 2004–2007 time period, which quantifies the geographical contributions to Toronto area O3. The important emission types for 15 pollution events are then determined with a high-resolution adjoint model. Toronto O3, during pollution events, is most sensitive to southern Ontario and U.S. fossil fuel NOx emissions and natural isoprene emissions. The sources of Toronto pollution events are found to be highly variable, and this is demonstrated in four case studies representing local, short-, middle-, and long-range transport scenarios. This suggests that continental-scale emission reductions could improve air quality in the Toronto region. We also find that abnormally high temperatures and high-pressure systems are common to all pollution events studied, suggesting that climate change may impact Toronto O3. Finally, we quantitatively compare the sensitivity of the surface and column measurements to anthropogenic NOx emissions and show that they are remarkably similar. This work thus demonstrates the usefulness of FTIR measurements in an urban area to assess air quality.

The Arctic is a region which despite the remoteness and lack of emission sources of pollutants, is one of the most affected by the long-range transport of pollution, which can affect background pollution levels and which influence climate change both regionally and globally. Despite improvements in observing systems and numerical models in recent decades, it remains difficult to reproduce the observed pollution episodes in the Arctic especially in summertime. One possible explanation is the underestimation of modelled ozone (O3) production in forest fires plumes. Carbon monoxide (CO) is often used as a tracer of pollution transport due to its relatively long lifetime of several weeks in the troposphere. It is a reactive gas, mainly produced by the combustion of fossil fuels and vegetation burning. Moreover, since its main sink is reaction with OH radical, CO has an important role in the oxidizing power of the atmosphere it also plays an important role in the assessment of tropospheric ozone. The purpose of my thesis has been to contribute to a better understanding of transport and of the chemical mechanisms of pollutants formation in the Arctic troposphere. A combination of the new CO measurements from the IASI satellite instrument, launched in October 2006 aboard the MetOp-A and aircraft data collected during the POLARCAT campaigns of the International Polar Year (IPY), in spring and summer 2008 were used. IASI CO observations were first validated by comparison with in situ airborne measurements showing its ability to detect the evolution of high CO signatures plume as close to sources regions. The second part of the thesis used assimilation of daily IASI CO measurements (Kalman filter) in the LMDz-INCA global model to improve our understanding about sources of pollution impacting the Arctic troposphere and their transport pathways. The assimilation has improved the modelling of CO pollution episodes in the Arctic free troposphere. Model results were also evaluated using POLARCAT observations and used to examine the sensitivity of Arctic pollutant concentrations (namely the overestimation of O3 distribution and the underestimation of PAN distribution) to emissions from different regions and in particular the boreal forest fire emissions., L'Arctique est une région qui malgré l'absence et l'éloignement de sources d'émission de polluants, est l'une des plus touchées par le transport à longue échelle de la pollution, qui peut affecter les niveaux de fond de pollution et qui influence le changement climatique à l'échelle régionale et mondiale. Malgré l'amélioration des systèmes d'observations et des modèles numériques durant ces dernières décennies, il reste encore difficile de reproduire les épisodes de pollution observés en Arctique notamment en été. Une explication possible est la sous-estimation de la production d'ozone (O3) modélisée dans les panaches des feux de forêt. Le monoxyde de carbone (CO) est utilisé comme un traceur du transport de la pollution du fait de sa longue durée de vie (plusieurs semaines) dans la troposphère. Ce gaz est produit par la combustion des énergies fossiles et des feux de biomasse. De plus, étant régulé par sa réaction avec le radical OH, il joue aussi un rôle important dans le bilan de l'O3 troposphérique. Le but de mes travaux de thèse a donc été de contribuer à une meilleure compréhension du transport et des mécanismes chimiques de formation des polluants secondaires dans la troposphère arctique. Pour cela j'ai utilisé en parallèle les nouvelles mesures de CO de l'instrument satellitaire IASI qui a été lancé en octobre 2006 à bord du satellite MetOp-A et les données récoltées par des avions instrumentés lors des campagnes POLARCAT de l'Année Polaire Internationale (API), au printemps et en été 2008. Les observations CO IASI ont tout d'abord été validées en les comparant avec les mesures aéroportées in situ montrant leurs capacités à observer des panaches de signatures élevées en CO comme près des régions sources. Le deuxième volet de la thèse illustre l'apport de l'assimilation (filtre de Kalman) des mesures quotidiennes de CO IASI dans le modèle global LMDz-INCA dans l'amélioration de notre compréhension sur les émissions et des chemins de transport des polluants influençant sur la troposphère arctique. L'assimilation a ainsi permis d'améliorer la modélisation des épisodes de pollution en CO dans la troposphère libre arctique. Enfin les résultats du modèle ont également été évalués en utilisant les observations POLARCAT et utilisés pour examiner la sensibilité des concentrations de polluants en Arctique (à savoir une surestimation de la distribution de l'O3 et une sous-estimation de celle du PAN) provenant des différentes régions et en particulier des feux de forêt boréale.

International audience; The advent of hyperspectral infrared instruments orbiting the Earth has allowed for detecting and measuring numerous trace gas species that play important roles in atmospheric chemistry and impact air quality, but for which there is a dearth of information on their distribution and temporal variability. Here we will present global and regional comparisons of measurements from the NASA TES and the European MetOp IASI instruments of three of these gases: ammonia (NH3), formic acid (HCOOH) and methanol (CH3OH). Ammonia is highly reactive and thus very variable in space and time, while the sources and sinks of methanol and formic acid are poorly quantified: thus space-based measurements have the potential of significantly increasing our knowledge of the emissions and distributions of these gases.IASI and TES have many similarities but some significant differences. TES has significantly higher spectral resolution (0.06 cm-1), and its equator crossing times are ~1:30 am and 1:30 pm, local time, while IASI has lower resolution (0.5 cm-1) and an earlier equator crossing time (9:30 am and 9:30 pm), which leads to lower thermal contrast; however IASI provides much greater temporal and spatial coverage due to its cross-track scanning. Added to the instrumental differences are the differences in retrieval algorithms. The IASI team uses simple but efficient methods to estimate total column amounts of the species above, while the TES team performs full optimal estimation retrievals.We will compare IASI and TES total column measurements averaged on a 2.5x2.5 degree global grid for each month in 2009, and we will examine the seasonal cycle in some regions of interest, such as South America, eastern China, and the Midwest and the Central Valley in the US. In regions where both datasets are in agreement this analysis will provide confidence that the results are robust and reliable. In regions where there is disagreement we will look for the causes of the discrepancies, which will lead to better algorithms, most immediately for the NPP CrIS instrument, which combines the coverage of IASI with the equator crossing time of TES.

International audience; An extremely severe and persistent smog episode occurred in January 2013 over China. The levels of air pollution have been dangerously high, reaching 40 times recommended safety levels and have affected health of millions of people. China faced one of the worst periods of air quality in recent history and drew worldwide attention. This pollution episode was caused by the combination of anthropogenic emissions and stable meteorological conditions (absence of wind and temperature inversion) that trapped pollutants in the boundary layer. To characterize this episode, we used the IASI (Infrared Atmospheric Sounding Interferometer) instrument onboard the MetOp-A platform. IASI observations show high concentrations of key trace gases such as carbon monoxide (CO), sulfur dioxide (SO2) and ammonia (NH3) along with ammonium sulfate aerosol. We show that IASI is able to detect boundary layer pollution in case of large negative thermal contrast combined with high levels of pollution. Our findings demonstrate the ability of thermal infrared instrument such as IASI to monitor boundary layer pollutants, which can support air quality evaluation and management.

International audience

International audience; Western Siberia has undergone a sharp increase in temperature during the last decades, modifying the biogeochemical and the hydrological cycles. Water vapor plays an important role in the atmosphere including in the radiative transfer, cloud formation and precipitation. Information about evaporation/condensation processes of water vapor can be provided by water stable isotopologues such as H216O and HDO. This study presents the joint H216O and HDO retrievals from Infrared Atmospheric Sounding Interferometer (IASI) spectra over Siberia. IASI is an instrument on board the MetOp-A European satellite launched in October 2006. The global coverage of this instrument and the good signal-to-noise ratio allow us to provide information on δD over this region. IASI measurements may be used to estimate integrated δD between the surface and 3 km altitude or from 1 to 5 km depending on the thermal contrast between the surface and the low troposphere. The retrieved data are compared to simulations from an isotopic GCM, LMDZiso, for 2011. The data show variations that are well correlated with the model at seasonal (r up to 0.8) and day-to-day (r≡0.6) time scales. The IASI-based retrievals and the model capture also well the seasonal variation of the specific humidity in the [0-3km] and the [1-5km] altitude ranges.

International audience; Urban areas are large sources of several air pollutants with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multi-channel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary later, is used, to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction of CO emission between 2000-2003 and 2004-2008, reaching -43% over Tehran and -47% over Baghdad. There is contrasted agreement between these results and the MACcity and EDGARv4.2 inventories.