Simulation and retrieval of atmospheric spectra using ASIMUT
Ann C Vandaele(1), Michel Kruglanski(1) and Martine De Mazière(1)
(1) Belgian Inst for Space Aeronomy, 3, av Circulaire, 1180 Brussels, Belgium
The ASIMUT software is line-by-line radiative transfer code coupled to an Optimal Estimation procedure to retrieve vertical profiles of atmospheric constituents, which has been developed to exploit the synergy existing between the growing number of different instruments working under different geometries. The main particularities of the software are:
(i) The possibility to retrieve columns and/or profiles of atmospheric constituents simultaneously from different spectra, which may have been recorded by different instruments or obtained under different geometries. This allows the possibility to perform combined retrieval, e.g., of a ground based measurement and a satellite-based one probing the same air mass, or from spectra recorded by different instruments on the same platform;
(ii) The analytical derivation of the Jacobians ;
(iii) The use of the Optimal Estimation method (OEM), using diagonal or full covariance matrices ;
(iv) Its portability;
(v) Its modularity, hence the ease to add future features. Initially developed for the Earth atmosphere, its applicability can be extended to extraterrestrial atmospheres.
As an additional development, the ASIMUT can be coupled to an algorithm to retrieve aerosol features from nadir thermal radiance spectra. Based on the vertical optical depths obtained with ASIMUT, this algorithm uses an OEM to retrieve both the aerosol optical thickness and the surface temperature, assuming a thin horizontal layer of a mixture of two aerosol types located at an arbitrary altitude in the troposphere.
Simulation and retrieval results for different case studies will be presented and compared to existing well established codes like LBLRTM and SFIT.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,