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Duc Dung TRAN (LMD)

Titre : Study of the absorption spectrum of oxygen in the near infrared and application to greenhouse gases remote sensing in the atmosphere


Lieu : En ligne
Membres du jury : 

François-Marie BRÉON (LSCE), President
Muriel LEPÈRE (LLS), Reviewer
Maud ROTGER (GSMA), Reviewer
Arnaud CUISSET (LPCA), Examiner
Solène TURQUETY (LMD), Examiner
Ha TRAN (LMD), Thesis Director
Juan CUESTA (LISA), Thesis Co-Director
Raymond ARMANTE (LMD), Thesis Co-Director

Résumé : 

This work is dedicated to the study of the spectroscopy of oxygen at 1.27 μm, in support of the satellite mission MicroCarb. Firstly, absorption spectra of air- and self-broadened O2 lines were first computed using requantized Classical Molecular Dynamics Simulations. Their fit using the quadratic speed-dependent Nelkin-Ghatak model provides high-order line-shape parameters that are consistent with experimentally determined values. The second part is devoted to the retrieval of the spectroscopic parameters of more than eighty lines of O2 broadened by air in the 1.27 μm band with the same model and the first-order line mixing. Validation of these line parameters, but also the Collision-Induced Absorption (CIA) coefficients available in literature for O2 were then performed and evaluated using the Spectroscopic Parameters And Radiative Transfer Evaluation calculation chain. The line parameters obtained in this thesis lead to much better agreement with measured spectra, compared to those obtained with the widely-used HITRAN and GEISA databases. The existing data of CIA coefficients lead to similar residuals, in rather good agreement with measurements. Finally, the first effects of line broadening by water vapor in the O2 A-band, and of the new oxygen spectroscopy data in the 1.27 μm band, on the retrievals of aerosols are studied using simulated spectra, for the same configurations of GOME-2 and MicroCarb measurements, respectively. The results show that neglecting the line broadening of O2 lines by H2O produces a very small error on the retrieval results using the O2 A-band. The sensitivity of the aerosol retrieval to O2 spectroscopy is relatively low for the 1.27 μm band.