Enhancing CRTM in Absorption, Single-scattering Properties, and Multiple Scattering Calculation with Polarization

Radiative transfer simulation is indispensable in satellite data assimilation applications. The multiple scattering computation is a key step for simulating radiative transfer. The accuracy of multiple scattering computation compared with realistic situation is determined by using a robust radiative transfer solver and appropriate cloud and aerosol single-scattering properties in conjunction with conducting accurate calculation of gaseous absorption.

This presentation will discuss recent advances in developing multiple scattering computational capabilities, including a newly developed vector radiative transfer model, improved dust aerosol and ice cloud particle single-scattering property models, and an efficient method to compute gaseous absorption. A two-component method that combines the small-angle approximation (SAA) and the adding-doubling method (AD) is developed to implement the multiple scattering calculations. A comprehensive radiative transfer package referred to as Texas A&M University vector radiative transfer model (TAMU-VRTM) accounts for gaseous absorption along with using SAA+AD to count for multiple scattering by particulate matters (cloud particles and aerosols). TAMU-VRTM is also capable of providing Jacobian matrix. In particular, the derivatives of the output Stokes vector versus the layer optical thicknesses and single-scattering albedos are derived analytically. The state-of-the-science invariant imbedding T-matrix (II-TM) method and the physical geometric optics method (PGOM) are utilized in the single-scattering property calculations because the II-TM and PGOM have an overlapping applicable size parameter range. This presentation will also show examples of the applications of the aforesaid vector radiative transfer capabilities. The developed computational programs and datasets can be directly used to enhance the capabilities of the Community Radiative Transfer Model (CRTM).