N2O Temporal Variability from the Middle Troposphere to the Middle Stratosphere Based on Airborne and Balloon-Borne Observations during the Period 1987–2018

Nitrous oxide (N2O) is the fourth most important greenhouse gas in the atmosphere and is considered the most important current source gas emission for global stratospheric ozone depletion (O3 ). It has natural and anthropogenic sources, mainly as an unintended by-product of food production activities. This work examines the identification and quantification of trends in the N2O concentration from the middle troposphere to the middle stratosphere (MTMS) by in situ and remote sensing observations. The temporal variability of N2O is addressed using a comprehensive dataset of in situ and remote sensing N2O concentrations based on aircraft and balloon measurements in the MTMS from 1987 to 2018. We determine N2O trends in the MTMS, based on observations. This consistent dataset was also used to study the N2O seasonal cycle to investigate the relationship between abundances and its emission sources through zonal means. The results show a longterm increase in global N2O concentration in the MTMS with an average of 0.89 ± 0.07 ppb/yr in the troposphere and 0.96 ± 0.15 ppb/yr in the stratosphere, consistent with 0.80 ppb/yr derived from ground-based measurements and 0.799 ± 0.024 ppb/yr ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) satellite measurements

N2_2O Temporal Variability from the Middle Troposphere to the Middle Stratosphere Based on Airborne and Balloon-Borne Observations during the Period 1987–2018

Nitrous oxide (N$_2$O) is the fourth most important greenhouse gas in the atmosphere and is considered the most important current source gas emission for global stratospheric ozone depletion (O$_3$). It has natural and anthropogenic sources, mainly as an unintended by-product of food production activities. This work examines the identification and quantification of trends in the N$_2$O concentration from the middle troposphere to the middle stratosphere (MTMS) by in situ and remote sensing observations. The temporal variability of N$_2$O is addressed using a comprehensive dataset of in situ and remote sensing N$_2$O concentrations based on aircraft and balloon measurements in the MTMS from 1987 to 2018. We determine N$_2$O trends in the MTMS, based on observations. This consistent dataset was also used to study the N$_2$O seasonal cycle to investigate the relationship between abundances and its emission sources through zonal means. The results show a long-term increase in global N$_2$O concentration in the MTMS with an average of 0.89 ± 0.07 ppb/yr in the troposphere and 0.96 ± 0.15 ppb/yr in the stratosphere, consistent with 0.80 ppb/yr derived from ground-based measurements and 0.799 ± 0.024 ppb/yr ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) satellite measurements

Characterisation of tropospheric pollution sources in the Mediterranean and West African regions by airborne in situ measurements and modelling

L’étude de la pollution troposphérique inclut l’étude des gaz traces provenant de sources anthropiquesdiverses, dont l’impact varie de l’échelle locale à globale. Pour caractériser cette pollution, il est nécessairede mesurer avec précision les concentrations en polluants. Dans le cadre de projets européens, troiscampagnes aéroportées ont été conduites, dans le bassin méditerranéen, en Afrique de l’ouest et enMalaisie, pour mesurer différents types de polluants grâce, entre autres, à un spectromètre à lasersinfrarouges, SPIRIT, capable de mesurer rapidement en ligne de faibles variations de NO2 et CO. Les jeuxde données de ces gaz traces (et d’autres) ont été combinés avec un modèle lagrangien de dispersion departicules, FLEXPART, pour identifier différentes sources de pollution locales et régionales de l’air. Cettethèse présente ainsi les mesures et le travail de modélisation entrepris afin de définir les sources depollution de chaque région. Il a été montré que le bassin méditerranéen a été impacté, de la moyenne à lahaute troposphère pendant l’été, par des émissions de feux de biomasse venant de Sibérie et du continentnord-américain. Les régions ouest-africaine et malaisienne sont aussi impactées par des émissions de feuxde biomasse transportées depuis l’Afrique centrale dans le premier cas, et de feux locaux dans le second.En outre, ces régions sont influencées par des émissions provenant de l’exploitation du pétrole et du traficmaritime. FLEXPART a été utilisé afin d’identifier l’origine des pics de pollution mesurés au cours descampagnes. Nous avons ainsi montré que les conditions atmosphériques, qui définissent la hauteurd’injection du panache de la plateforme pétrolière, ainsi que le flux d’émission sont des paramètres clésdans la caractérisation des mesures par le modèle.The study of tropospheric pollution includes the study of trace gases coming from various anthropogenicsources that can impact scales ranging from local to global. To characterise this pollution, it is necessary tobe able to measure with precision pollutant concentrations. Within the frame of European projects, threeairborne campaigns in the Mediterranean Basin, in West Africa and in Malaysia were conducted to measuredifferent types of pollutants thanks to, among others, an infrared laser spectrometer, SPIRIT, able to rapidlymeasure on-line small variations in NO2 and CO. The data sets of these trace gases (and others) have beencombined with a Lagrangian model of particle dispersion, FLEXPART, to fingerprint different sources of localand regional air pollution. Thus, this thesis presents the measurements and the modelling work undertakenin order to define the sources of pollution of each region. It has been shown that the Mediterranean Basinwas impacted, in the mid to upper troposphere during summer, by biomass burning emissions coming fromSiberia and the Northern American continent. West African and Malaysian regions are also impacted bybiomass burning emissions transported from central Africa in the first case, and from local fires in thesecond. In addition, those regions are influenced by emissions coming from oil exploitation and maritimetraffic. FLEXPART was used in order to identify the origin of the pollution peaks measured during thecampaigns. It has been shown that atmospheric conditions, which define the injection height of the oilplatform plume, and also the emission flux are key parameters in the characterisation of the measurementsby the model

Caractérisation de sources de pollution troposphérique en régions méditerranéenne et ouest-africaine par mesures in situ en avion et modélisation.

The study of tropospheric pollution includes the study of trace gases coming from various anthropogenicsources that can impact scales ranging from local to global. To characterise this pollution, it is necessary tobe able to measure with precision pollutant concentrations. Within the frame of European projects, threeairborne campaigns in the Mediterranean Basin, in West Africa and in Malaysia were conducted to measuredifferent types of pollutants thanks to, among others, an infrared laser spectrometer, SPIRIT, able to rapidlymeasure on-line small variations in NO2 and CO. The data sets of these trace gases (and others) have beencombined with a Lagrangian model of particle dispersion, FLEXPART, to fingerprint different sources of localand regional air pollution. Thus, this thesis presents the measurements and the modelling work undertakenin order to define the sources of pollution of each region. It has been shown that the Mediterranean Basinwas impacted, in the mid to upper troposphere during summer, by biomass burning emissions coming fromSiberia and the Northern American continent. West African and Malaysian regions are also impacted bybiomass burning emissions transported from central Africa in the first case, and from local fires in thesecond. In addition, those regions are influenced by emissions coming from oil exploitation and maritimetraffic. FLEXPART was used in order to identify the origin of the pollution peaks measured during thecampaigns. It has been shown that atmospheric conditions, which define the injection height of the oilplatform plume, and also the emission flux are key parameters in the characterisation of the measurementsby the model.L’étude de la pollution troposphérique inclut l’étude des gaz traces provenant de sources anthropiquesdiverses, dont l’impact varie de l’échelle locale à globale. Pour caractériser cette pollution, il est nécessairede mesurer avec précision les concentrations en polluants. Dans le cadre de projets européens, troiscampagnes aéroportées ont été conduites, dans le bassin méditerranéen, en Afrique de l’ouest et enMalaisie, pour mesurer différents types de polluants grâce, entre autres, à un spectromètre à lasersinfrarouges, SPIRIT, capable de mesurer rapidement en ligne de faibles variations de NO2 et CO. Les jeuxde données de ces gaz traces (et d’autres) ont été combinés avec un modèle lagrangien de dispersion departicules, FLEXPART, pour identifier différentes sources de pollution locales et régionales de l’air. Cettethèse présente ainsi les mesures et le travail de modélisation entrepris afin de définir les sources depollution de chaque région. Il a été montré que le bassin méditerranéen a été impacté, de la moyenne à lahaute troposphère pendant l’été, par des émissions de feux de biomasse venant de Sibérie et du continentnord-américain. Les régions ouest-africaine et malaisienne sont aussi impactées par des émissions de feuxde biomasse transportées depuis l’Afrique centrale dans le premier cas, et de feux locaux dans le second.En outre, ces régions sont influencées par des émissions provenant de l’exploitation du pétrole et du traficmaritime. FLEXPART a été utilisé afin d’identifier l’origine des pics de pollution mesurés au cours descampagnes. Nous avons ainsi montré que les conditions atmosphériques, qui définissent la hauteurd’injection du panache de la plateforme pétrolière, ainsi que le flux d’émission sont des paramètres clésdans la caractérisation des mesures par le modèle

Anthropogenic plumes from metropolitan areas and biomass burning emissions in West Africa during DACCIWA - airborne measurements on board the DLR Falcon 20

International audienceThe DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions over West Africa) airborne field campaign was conducted in Southern West Africa in June/July 2016. Three European research aircraft (DLR - Falcon 20, SAFIRE - ATR 42 and BAS - Twin Otter) were deployed from Lomé/Togo and conducted research flights across Ivory Coast, Ghana, Togo and Benin. On board the DLR Falcon O3, SO2, CO, NO2 and aerosol fine mode particle number concentration and size distribution were measured during a total of 12 scientific flights. Until now only few airborne trace gas measurements were conducted in Southern West Africa. Therefore, this field experiment contributes to the knowledge of the chemical composition of the lower troposphere between 0 - 4 km. During several flights pollution plumes from major population centers - Lomé/Togo, Accra/Ghana, Kumasi/Ghana, and Abidjan/Ivory Coast - were probed below, inside and above clouds. Here, enhanced trace gas and particle concentrations were observed. In addition, plumes from biomass burning emissions were detected which were transported to West Africa. The composition of the pollution plumes are presented as well as transport pathways using HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectories) trajectory calculations. Ozone enhancements in the biomass burning pollution plumes of up to 70 ppb were observed compared to background concentrations of 30-40 ppb. Furthermore, HYSPLIT atmospheric dispersion simulations are used to estimate anthropogenic SO2 city emissions

Trace gas profiles and anthropogenic plumes from metropolitan areas in West Africa during DACCIWA - Airborne measurements on board the DLR Falcon 20

International audienceThe DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions over West Africa) airborne field campaign was conducted in Southern West Africa in June/July 2016. The atmosphere in South West Africa is exposed to numerous influences like the Monsoon, biomass burning and oil rigs. Its chemical composition is modified by urbanisation, a growing population, complex meteorological influences and air pollution. During DACCIWA, three European research aircraft (DLR - Falcon 20, SAFIRE - ATR 42 and BAS - Twin Otter) were deployed from Lomé/Togo and conducted research flights across Ivory Coast, Ghana, Togo and Benin. On board the DLR Falcon O3, SO2, CO, NO2 and aerosol fine mode particle number concentration and size distribution were measured during a total of 12 scientific flights. Distinct trace gas layers were found during vertical soundings. An O3 layer at 3000 m altitude was observed during 6 flights with concentrations up to 85 ppb compared to background concentrations of about 35 ppb due to southern hemispheric biomass burning products which were transported to the DACCIWA study area. Furthermore, enhanced trace gas and particle number concentrations were detected in city pollution plumes of Lomé/Togo, Accra/Ghana and Kumasi/Ghana. O3 enhancements of 5 - 10 ppb were measured downstream of the cities relative to the upstream observations. Measured SO2 pollution plumes with concentrations up to 0.9 ppb near Lomé are combined with HYPSLIT dispersion simulations and are compared to emission databases

Anthropogenic plumes from metropolitan areas and biomass burning emissions in West Africa during DACCIWA - airborne measurements on board the DLR Falcon 20

International audienceThe DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions over West Africa) airborne field campaign was conducted in Southern West Africa in June/July 2016. Three European research aircraft (DLR - Falcon 20, SAFIRE - ATR 42 and BAS - Twin Otter) were deployed from Lomé/Togo and conducted research flights across Ivory Coast, Ghana, Togo and Benin. On board the DLR Falcon O3, SO2, CO, NO2 and aerosol fine mode particle number concentration and size distribution were measured during a total of 12 scientific flights. Until now only few airborne trace gas measurements were conducted in Southern West Africa. Therefore, this field experiment contributes to the knowledge of the chemical composition of the lower troposphere between 0 - 4 km. During several flights pollution plumes from major population centers - Lomé/Togo, Accra/Ghana, Kumasi/Ghana, and Abidjan/Ivory Coast - were probed below, inside and above clouds. Here, enhanced trace gas and particle concentrations were observed. In addition, plumes from biomass burning emissions were detected which were transported to West Africa. The composition of the pollution plumes are presented as well as transport pathways using HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectories) trajectory calculations. Ozone enhancements in the biomass burning pollution plumes of up to 70 ppb were observed compared to background concentrations of 30-40 ppb. Furthermore, HYSPLIT atmospheric dispersion simulations are used to estimate anthropogenic SO2 city emissions

Trace gas profiles and anthropogenic plumes from metropolitan areas in West Africa during DACCIWA - Airborne measurements on board the DLR Falcon 20

International audienceThe DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions over West Africa) airborne field campaign was conducted in Southern West Africa in June/July 2016. The atmosphere in South West Africa is exposed to numerous influences like the Monsoon, biomass burning and oil rigs. Its chemical composition is modified by urbanisation, a growing population, complex meteorological influences and air pollution. During DACCIWA, three European research aircraft (DLR - Falcon 20, SAFIRE - ATR 42 and BAS - Twin Otter) were deployed from Lomé/Togo and conducted research flights across Ivory Coast, Ghana, Togo and Benin. On board the DLR Falcon O3, SO2, CO, NO2 and aerosol fine mode particle number concentration and size distribution were measured during a total of 12 scientific flights. Distinct trace gas layers were found during vertical soundings. An O3 layer at 3000 m altitude was observed during 6 flights with concentrations up to 85 ppb compared to background concentrations of about 35 ppb due to southern hemispheric biomass burning products which were transported to the DACCIWA study area. Furthermore, enhanced trace gas and particle number concentrations were detected in city pollution plumes of Lomé/Togo, Accra/Ghana and Kumasi/Ghana. O3 enhancements of 5 - 10 ppb were measured downstream of the cities relative to the upstream observations. Measured SO2 pollution plumes with concentrations up to 0.9 ppb near Lomé are combined with HYPSLIT dispersion simulations and are compared to emission databases

A Database of Aircraft Carbon Monoxide (CO) Measurements with High Temporal and Spatial Resolution during 2011 - 2021

International audienceTo understand tropospheric air pollution at a regional/global scale, the SPIRIT airborne instrument (SPectromètre Infra-Rouge In situ Toute altitude) was developed in 2011 and used on aircraft to measure CO, an important indicator of air pollution, during the last decade. SPIRIT could provide high-quality CO measurements with 1σ precision of 0.3 ppbv at a time resolution of 1.6 s. It can be operated on different aircraft from DLR (Germany) and SAFIRE (CNRS-CNES-Météo France) such as Falcon-20 and ATR-42. With support from various projects, more than 200 flight hours measurements were conducted over three continents (Europe, Asia, Africa), including two inter-continental transect measurements (Europe-Asia and Europe-Africa). Levels of CO and its horizontal and vertical distribution are briefly discussed and compared between different regions/continents. A 3D trajectory mapped by CO level was plotted for each flight and presented in this study. The database containing all the raw data will be archived on the AERIS database (www.aeris-data.fr), the French national center for Earth observation dedicated to the atmosphere. The database can help to understand the horizontal and vertical distribution of CO over different regions and continents. Besides, it can help to validate model performance and satellite measurements. For instance, the database covers measurements at high-latitude regions (i.e., Kiruna, Sweden, 68˚N) where satellite measurements are still a challenge, and at low-latitude regions (West Africa and South-East Asia) where in situ data are scarce and satellites need more validation by airborne measurements

Atmospheric Pollution from Shipping and Oil platforms of West Africa (APSOWA) observed during the airborne DACCIWA campaign

International audienceIn the framework of the European DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) project, the airborne study APSOWA (Atmospheric Pollution from Shipping and Oil platforms of West Africa) has been conducted in July 2016 to study emissions from oil rigs and maritime traffic in the Gulf of Guinea. The measurements were performed during four flights of about 3-4 hours including meandering transects through emission plumes in the planetary boundary layer (around 300 m asl) off the coast of West Africa from Ivory Coast to Togo. Several instruments have been used on-board the DLR Falcon-20, providing measurements of the pollutants O3, CO, NO2, SO2, aerosol content and meteorological parameters. This set of trace gases can be used to fingerprint different sources of local air pollution. The first part of our study is focused on the FPSO Kwame Nkrumah facility operating in the Jubilee oil field off the coast of Ghana. Aircraft observations have been combined with a nested-grid regional scale Lagrangian particle dispersion model (FLEXPART) to estimate surface emission fluxes from this platform. A simplified inverse method is used and repeated until the modelling output and aircraft observations converged. The estimated fluxes of CO, SO2, NO2 are compared to global (EDGAR, MACCity) and regional (Deetz and Vogel, 2017, in press) inventories. A second part of the study provides the first results of the APSOWA flights for the study of the impact of shipping emissions on the regional air quality. Using data from Marine Traffic, ship positions during the campaign are identified. Then, FLEXPART is used to quantify the contributions of the ship emissions to the aircraft observations. Finally, direct measurements in the MBL around 4°N latitude along the Ghana coast show no strong evidence of the presence of an atmospheric pollution maritime corridor simulated by MACCity