Line-by-line computations with polarization and scattering are very demanding. Discrete ordinate methods require much computation time and memory, because the linear equation system to be solved becomes very large (check papers!!!). Using the Monte Carlo method with importance sampling polarized line-by-line calculations are very efficient and don't need much memory.
The method has been implemented in MYSTIC, spectral absorption and extinction coefficients are corrected by an importance sampling method. This method is exact for a clearsky atmosphere, in case of cloud, also the phase matrix need to be corrected (which is already implemented but not yet carefully checked.)
A test calculation has been performed in the O2A band, 1e9 photons were used for an accurate comparison with disort.
Tests for various spectral regions corresponding to channels of the GOSAT FTR instrument (http://www.gosat.nies.go.jp/index_e.html).
Calculations are for TOA radiances with different amount of aerosol and cirrus (motivation for simulating this … ). The polarization characteristics of the underlying surface can not be neglected, for this study a water surface (BPDF by Mishchenko).
Results, accurracy, CPU times …