GEISA-97 Introduction |
Adequate tools are required to perform reliable radiative transfer calculations to meet the needs of communities involved in understanding the atmospheres of the Earth and other planets. In particular, accurate spectral analyses of Earth or planetary spectra observed by new generations of high spectral resolution vertical atmospheric sounders will result in an improved knowledge of their atmospheric and surface properties. The performance of instruments like AIRS (Atmospheric Infrared Sounder) in the USA (JPL, 1991), and IASI (Infrared Atmospheric Sounding Interferometer) in Europe (Phulpin et al., 1997), which have a better vertical resolution and accuracy compared to presently existing satellite infrared temperature sounders, is directly related to the quality of the spectroscopic parameters of the optically active atmospheric gases since these are essential input in the forward models used to simulate recorded radiance spectra. The ARA (Atmospheric Radiation Analysis) group at LMD (Laboratoire de Météorologie Dynamique du CNRS, France) developed the GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information) computer accessible database system (Chedin et al., 1982; Husson et al., 1992, 1994), in 1974. This early effort implemented the so-called line-by-line and layer-by-layer approach for forward radiative transfer modeling action. This activity is of interest to research groups involved in direct and inverse radiative transfer studies.
The role of molecular spectroscopy in modern atmospheric research has entered a new phase with the advent of highly sophisticated spectroscopic instruments and computers. Retrieval of the concentrations of radiatively active molecular species from observed spectra of planetary atmospheres using available spectroscopic databases and atmospheric models has become fairly routine. The molecular spectroscopist is constantly on demand to deliver data that are not only appropriate but essential for the analyses of the planetary atmospheric observations. GEISA is dedicated to meeting that aim.
Currently, GEISA is involved in activities, with the purpose of assessing the IASI (Infrared Atmospheric Sounding Interferometer) measurement capabilities and its own database quality, within the ISSWG (IASI Sounding Working Group), in the frame of the CNES (Centre National d'Etudes Spatiales, France)/EUMETSAT (EUropean organization for METeorological SATellites) European Polar System (EPS), by simulating high-resolution adiances and/or using experimental data, as described in Jacquinet-Husson et al., 1998a.