Recent Improvements to the Community Radiative Transfer Model (CRTM)

The community radiative transfer (RT) model (CRTM) is developed by the US Joint Center for Satellite Data Assimilation (JCSDA) for rapid satellite radiance simulations and radiance derivative calculations under various sky and surface conditions. It is a key component of the Gridpoint Statistical Interpolation (GSI) data assimilation system at the NOAA National Center for the Environmental Prediction (NCEP) Environmental Modeling Center (EMC) and systems at other Numerical Weather Prediction (NWP) centers, as well as in many other satellite radiance data applications. The model has been recently upgraded from version 1.2 to version 2.0.2. In this presentation, we will summarize our progress in the development of the CRTM model with a focus on the improvements that have been or will soon be implemented in CRTM version 2 and are significant to the applications of the sensors on the future national operational environmental satellite systems, in particular the Joint Polar Satellite System (JPSS) and the Geostationary Operational Environmental Satellite R-Series (GOES-R). The progress includes an improved atmospheric gas transmittance model , an improved microwave ocean surface model, a new bi-directional reflection distribution function (BRDF) for calculations of solar ocean surface reflection, a new module for corrections of the Non Local Thermodynamic Equilibrium (NLTE) effect for IR sensors, and a new component for Visible/Ultraviolet sensors. A module to compute radiances for microwave channels that are affected by Zeeman-splitting will also be discussed for its potential application in the JPSS system.