The CRTM transmittance coefficient package

• A comprehensive description of the CRTM instrument coefficient generation process and software package is provided. • The operational context and the theoretical radiative transfer background of the process are examined. • The workflow and structure of the line-by-line radiative transfer computations is outlined. • Several recent CRTM instrument application examples are showcased. The CRTM transmittance coefficient generation package is a high-performance computing workflow to generate spectral and transmittance coefficients for the JCSDA Community Radiative Transfer Model (CRTM), which is used as an observation operator in satellite data assimilation applications. The characteristics of new instruments, whose observations are modeled by the CRTM, are encapsulated in these aforementioned coefficient data structures. This approach is a key factor in achieving the necessary high computational speeds with the CRTM. Complex atmospheric transmittance spectra in particular are approximated using the ODPS and ODAS algorithms. The transmittance coefficient generation package for the first time provides a unified and reproducible workflow to CRTM generate coefficients.