Etude de la variabilité de la vapeur d'eau dans la haute troposphère-basse stratosphère tropicale et du monoxyde de carbone troposphérique à partir d'observations spatiales

La tropopause tropicale est une région de l'atmosphère où l'abondance de vapeur d'eau (H2O) affecte le climat. Cette thèse examine le rôle de la convection profonde sur la variabilité de H2O dans cette région. En se basant sur les observations de l'instrument spatial Microwave Limb Sounder (MLS), je montre que la convection continentale impacte le cycle diurne de H2O par injection de cristaux de glace hydratant après sublimation cette région de l'atmosphère. Dans le cadre du projet TRO-pico, je présente aussi un cas d'étude en se focalisant sur le Sud du Brésil. J'analyse également la variabilité du monoxyde de carbone (CO) troposphérique grâce à l'Atmospheric InfraRed Sounder (AIRS). Cette étude est complétée par l'évaluation de la version 6 des inversions de AIRS et de la fusion de données combinant les observations de AIRS à celles du Tropospheric Emission Spectrometer (TES) et MLS. Je démontre ainsi la valeur ajoutée de ces produits pour des études liées à la qualité de l'air, la dynamique et le transport dans la haute troposphère-basse stratosphère.The Tropical Tropopause Layer (TTL) is a key region of the atmosphere where abundance of water vapor (H2O) can affect the climate. In this thesis, I address the question of the impact of deep convection on the H2O variability in the TTL. Based on the space-borne Microwave Limb Sounder (MLS) observations, I show that the continental convection drives the H2O diurnal variability in the TTL where the sublimation of ice crystals injected by overshoots has a moistening effect. As part of the TRO-pico project, I also emphasize the results obtained in southern Brazil. I also analyze the tropospheric carbon monoxide (CO) variability derived from the Atmospheric InfraRed Sounder (AIRS) measurements. This study is completed by the validation of the AIRS CO operational product version 6, and that of the data fusion combining observations from AIRS with the Tropospheric Emission Spectrometer (TES) and MLS, providing valuable information for air quality, upper troposphere-lower stratosphere dynamics and transport studies

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements