The Community Radiative Transfer Model (CRTM) is a sensor-based fast radiative transfer model developed at the Joint Center for Satellite Data Assimilation (JCSDA). The CRTM simulates satellite-based radiances and radiance gradients (or Jacobians) over various atmospheric and surface conditions and has several applications. Currently, the CRTM is used within the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical interpolation (GSI) global data assimilation system, the Global Modeling and Assimilation Office (GMAO) reanalysis system, the Weather Research and Forecasting (WRF) model, the Microwave Integrated Retrieval System (MIRS), and the Advanced Clear-Sky Processor for Oceans (ACSPO) retrieval system.

In this presentation, we will provide an overview of the CRTM with a focus on the improvements that have been or will soon be implemented in CRTM. The model includes a multiple transmittance algorithm framework, which allows different transmittance algorithms to coexist, such as the OPTRAN algorithm (Optical Path TRANsmittance), and the ODPS algorithm (Optical Depth in Pressure Space). In addition, special algorithms are implemented to take into account Zeeman-splitting effect for the SSMIS and AMSU-A sensors, CO2 cell pressure leaking effect for the Stratospheric Sounding Unit (SSU), and corrections of the Non Local Thermodynamic Equilibrium (NLTE) effect for IR sensors. In regards to surface optics updates we will describe the implementation of a physical microwave land surface emissivity model and a new microwave sea surface emissivity model (FASTEM5). We are evaluating several microwave and infrared land surface emissivity databases in CRTM. Additionally, we will describe the integration of the Successive Order of Interaction (SOI) radiative transfer model.