Ice hydrometeor microphysical assumptions in radiative transfer models at AMSU-B frequencies

Comparisons between two radiative transfer models, ARTS and RTTOV, showed that results in the presence of scattering from ice hydrometeors are highly dependent on assumptions made about the ice microphysics, specifically the size distribution and the density of the ice particles. This paper presents the results of a comparison study between a number of different treatments for the ice microphysics in RTTOV. Of the approaches considered, the combination of a size-dependent density (larger ice particles are less dense) and a size distribution treatment based on the cloud temperature and ice water content give the best approximation for the cases examined. Further work is planned in other regimes to see if this approach can be applied more widely. (C) Crown Copyright 2007. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.