Validation of Shortwave Infrared Sea Surface Reflection and Non-Local Thermodynamic Equilibrium Effects in Community Radiative Transfer Model Using IASI Data

The satellite radiances at shortwave infrared channels from 1.0 to 4.3 μm are not assimilated in numerical weather prediction data assimilation systems and not adequately corrected for applications of temperature retrieval. During the daytime, the shortwave infrared window channel radiance over ocean is strongly affected by the reflected solar radiance, which can contribute as much as 20.0 K to the measured brightness temperatures (BT). The Non-Local Thermodynamic Equilibrium (NLTE) emission at 4.3 μm CO2 region can produce additional 10 K to the measured BT. In this study, a bi-directional reflection distribution function (BRDF) model over ocean and a radiance correction scheme on the effects of NLTE for hyper-spectral sensors are implemented in the Community Radiative Transfer Model (CRTM). These improved capabilities allow satellite assimilation systems and retrieval algorithms to use the shortwave window channels for lower-air soundings and CO2 channels for upper-air soundings. Model biases and standard deviations between Infrared Atmospheric Sounding Interferometer (IASI) observation data and CRTM simulations are greatly improved for daytime, and are very close to nighttime.