The European megacity of Paris, with its 11 million inhabitants, offers a unique platform for the study of atmospheric composition and air quality. Since 2007, we have been using a high spectral resolution Fourier Transform Spectrometer (FTS-Paris) to monitor the composition of the atmosphere over Paris. Measurement configurations can be switched between near-infrared observations for the Total Carbon Column Observing Network (TCCON), of which FTS-Paris has been an official member since 2014, and thermal infrared observations within the frame of the Network for the Detection of Atmospheric Composition Change Infrared Working Group (NDACC-IRWG).

The main objective of this thesis work is to qualify the Paris site as a new NDACC-IRWG measurement station in a European megacity. It was thus necessary to implement NDACC-IRWG recommended retrieval strategies for analysing the atmospheric spectra recorded by the FTS-Paris instrument. The retrieval of atmospheric trace gas abundances had also to comply with the specifications imposed by the NDACC-IRWG network. We present these inversion strategies with the SFIT4 radiative transfer code, as well as long time series of total columns of NDACC-IRWG standard products (CO, C₂H₆, HCl, N₂O, CH₄, HF and HCN) and non-standard products (H₂CO, NO₂ and OCS). These results have allowed the Paris site to join the NDACC network in 2024.

In addition to the long-term climatology of the NDACC products, an analysis of 10 years of back-trajectories from the HYSPLITT model was carried out and used to describe the wind patterns (direction, frequence) at Paris in order to characterise the site at Jussieu. These back trajectories help to understand observed variations of de-seasonalized total columns of carbon monoxide (ΔCO) and ethane (ΔC₂H₆). Episodes with extreme ΔCO and ΔC₂H₆ values, corresponding to clean and polluted air masses, are analysed and discussed. Using simple kinetic modelling, we compare the seasonal variations of the ratio between CO and C₂H₆ total columns to the corresponding emission ratio.

Lieu
Sorbonne Université – Campus Pierre et Marie Curie
4, place Jussieu 75005 PARIS
Amphi Durand (bât. Esclangon)

Visio
https://cnrs.zoom.us/j/95040482404?pwd=pdpr1iiSBurbz5W7EslqagjgUKUaod.1

• Pascale Chelin, Maître de Conférences HDR de l’Université Paris-Est Créteil (Rapportrice)
• Thomas Lauvaux, Professeur de l’Université de Reims Champagne-Ardenne (Rapporteur)
• Martine De Mazière, Directrice de Recherche IASB (Examinatrice)
• Minqiang Zhou, Associate Professor of Chinese Academy of Sciences (Examinateur)
• Hèlène Chepfer, Professeure de Sorbonne Université (Présidente du jury)
• Yao Té, Maître de Conférences HDR de Sorbonne Université (Directeur de thèse)
• Christof Janssen, Chargé de Recherche du CNRS (Co-encadrant invité)