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Accueil > Séminaires > Archive des séminaires d’Utinam > 2014

Nina Lavrentieva

Spectroscopic databases for the terrestrial and planetary atmospheres modelling

mardi 11 mars 2014, 14h00

salle de conférences de l’observatoire

Nina Lavrentieva, V.E. Zuev Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences, 1 Akademishian Zuev square, 634021 Tomsk, Russie

professeur invité à l’Université de Franche Comté
(voir le programme complet du cours)

Résumé :

Modern spectroscopic databases for the Earth’s atmosphere, such as HITRAN and GEISA, are the worldwide standards for calculating or simulating atmospheric radiative transfer from the microwave to the ultraviolet spectral regions. They are computer-accessible, designed to facilitate accurate forward radiative transfer calculations using a line-by-line and layer-by-layer approach. The current version of HITRAN contains 42 molecular species with their most significant isotopologues.

In the Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science (IAO SB RAS) the compilation of spectroscopic databases and information systems are developed. In cooperation with French colleagues (GDRI SAMIA 2009-2012), a cycle of works on the global simulation of high-resolution rotational-vibrational spectra of carbon dioxide, nitrogen monoxide, ozone, acetylene, and hydrogen sulfur molecules has been carried out. The created models describe positions and intensities of spectral lines of both low-temperature and high-temperature spectra of these molecules with the nearly experimental accuracy. The simulation has allowed the compilation of the data bank (CDSD) on high-resolution spectra of the carbon dioxide molecule (ftp://ftp.iao.ru/pub/CDSD-2008/). In its characteristics, this data bank is superior to the well-known HITRAN, HITEMP, and GEISA databases. The CDSD data bank has allowed the assignment of several new bands of carbon dioxide in the spectrum of the Venus atmosphere recorded by the European Venus Express satellite.

In cooperation with the St. Petersburg University and the Institute of Applied Physics RAS, the distributed information system on molecular spectroscopy (http://wadis.iao.ru, http://atmos.molsp.phys.spbu.ru/, http://atmos.appl.sci-nnov.ru/) for collection and processing of primary information about measured and calculated spectral characteristics of atmospheric molecules has been developed. In this system, an emphasis is put on the data sources in molecular spectroscopy in order to obtain the adequate and reliable information on both molecular parameters and their primary sources. In cooperation with some foreign universities, the W@DIS information system is being developed. This system concerns the spectroscopy of water and is a prototype for the development of distributed international systems on atmospheric spectroscopy.

In cooperation with colleagues from the University of Franche-Comte (LIA SAMIA 2013-2016) we investigate pressure-dependent line profile parameters induced by collisions with atmospheric gases. Namely, broadening and shifting coefficients are searched for as a function of collision partner and temperature. The available experimental data are insufficient, and HITRAN, GEISA and other databases have to be expanded and supplemented with a large amount of theoretical data. Rather complicated versions of the cut-off-free method describe the line broadening processes rather well, but due to the complexity of the calculations, do not allow visualizing and analyzing processes occurring in colliding molecules, in particular, the effect of compensation for contributions of different scattering channels in the pressure-induced shift. A very efficient semi-empirical method has been developed in the Institute of Atmospheric Optics to calculate broadening and shifting coefficients of spectral lines and their temperature exponents. It includes correction factors whose parameters can be determined by fitting the calculated broadening or shifting coefficients to experimental data. The efficiency of the method is demonstrated with the examples of CO2 and H2O spectral lines, as well as with some applications to planetary atmosphere modelling.