The Community Radiative Transfer Model (CRTM) Development for Active and Hyperspectral Sensors.

The CRTM is a fast model to calculate satellite observed radiance and its sensitivity to atmospheric and surface state variables in UV, VIS, IR and MW spectral regions. It is widely used as an observation operator for radiance data assimilation, satellite-based retrieval system, remote sensing algorithm development and for cal/val applications in the community. In CRTM, atmospheric gas absorption is calculated in sensor-channel base using regressing methods fitting to line-by-line calculations. Scattering radiative transfer (RT) is calculated with Advanced Doubling‐Adding (ADA) algorithm. It also includes a comprehensive set of models for surface emissivity and reflectivity over land, ocean, ice and snow surfaces. Correction algorithms are implemented for the Non Local Thermodynamic Equilibrium (NLTE) effects and Zeeman-splitting effect. The tangent-linear and adjoint/K-matrix are implemented with algorithm differentiation method.

Recent developments in CRTM include extending the Advanced Doubling-Adding (ADA) method to incorporate full Stokes polarization calculations; and providing support for new sensors deployed on various satellite missions, such as JPSS-2, GOES-18, GOES-19, MetOp-SG, MTG, and upcoming SmallSats. In our presentation, we delve into CRTM’s progress in simulating active sensors and hyperspectral microwave instruments. Noteworthy achievements involve generating transmittance coefficients for cloudSAT and the Global Precipitation Measurement (GPM) Dual-Frequency Precipitation Radar (DPR), as well as simulating radar reflectivity using CRTM. Additionally, CRTM’s enhancement in generating and evaluating coefficients for Hyper-MW sensors will be reported as well. CRTM plays a pivotal role in evaluating commercial satellite microwave data for NWP applications.