Optimizing the CRTM for Improved Performance of All-Sky Radiance Data Assimilation

The goals of this 2-yr JCSDA project are to determine the optimum configuration of fast analytic radiative transfer (RT) solvers for rapid and accurate calculation of all-sky microwave and infrared radiances in the Community Radiative Transfer Model (CRTM) and demonstrate the impact of these improvements on the NASA Goddard Earth Observing System Model, Version 5 (GEOS-5) data assimilation system. This study highlights the first year of the project, which includes integrating some of the fastest (RT) solvers available for scattering atmospheres, including the delta-Eddington approximation and an improved polarized 2-stream solution, into the CRTM and, based on results of an earlier JCSDA project, objectively find the fastest solver for a given degree of scattering and desired accuracy. The impact of these improvements on forward RT calculations for GEOS-5 and Global Forecast System (GFS) model fields will be shown for the Global Precipitation Measurement Microwave Imager (GMI) and Cross-track Infrared Sounder (CrIS).