A FAST AND ACCURATE METHOD OF CALCULATION OF GASEOUS TRANSMISSION FUNCTIONS IN PLANETARY-ATMOSPHERES

A new method of calculation of atmospheric transmittance in planetary atmospheres is discussed. The gaseous absorption coefficient is repres ented as a product of two functions: k(p, T, nu) = G(p) . F(T,nu), whe re time consuming line-by-line calculations are involved in F(T, nu). They are performed only once on a specified temperature and wave numbe r grid. This created matrix is then used for fast interpolative determ ination of the absorption coefficient at any atmospheric level. The be haviour of this algorithm is studied for both Lorentz and Voigt line p rofiles. Test calculations for the 15 mu m CO2 band for the conditions typical for the Earth, Mars and Venus atmospheres are presented. This method combines speed and accuracy and can be effectively used in a w ide range of atmospheric studies: thermal sounding, quantitative spect roscopy, radiative energy balance calculations. (C) 1997 Elsevier Scie nce Ltd.