Fast Computation of Monochromatic Infrared Atmospheric Transmittances Using Compressed Look-Up Tables

We present a new technique for the fast computation of near-monochromatic atmospheric transmittances in the infrared, utilizing compressed lookup tables, that is well suited for nadir viewing satellite and airplane observations. The algorithm is very simple to use in radiative transfer codes and is easily adapted to provide analytic Jacobians of radiances. A Singular Value Decomposition (SVD) is used to transform very large monochromatic lookup tables of optical depths into a compressed representation that is approximately 73 times smaller. Temperature and pressure interpolations are performed in the compressed representation, resulting in significant savings in computation times. The resulting transmittances are as accurate as those computed with a line-by-line algorithm.