A fast radiance simulator for the Visible Infrared Imaging Radiometer Suite (VIIRS)

A fast radiance simulator is developed to model observations made by the Visible Infrared Imaging Radiometer Suite (VIIRS) in both clear and cloudy atmospheres. Atmospheric absorption is accounted for using the correlated k-distribution model (CKD) with the VIIRS spectral response functions considered. A novel feature of this fast model is that VIIRS cloudy sky radiances for the solar channels are simulated through application of pre-calculated lookup tables (LUTs) of the bidirectional reflection and transmission functions for water and ice clouds. Ice cloud bulk scattering properties are derived using the most recent version of the Yang group's nonspherical ice crystal single-scattering property database.

In this study, we will demonstrate the accuracy and efficiency of the VIIRS fast radiance simulator in comparison with a combination of the rigorous line-by-line (LBL) and discrete ordinate radiative transfer (DISORT) models. The simulated reflectances for cloudy sky scenes will be compared to VIIRS observations. Furthermore, we will show that the simulated reflectances can be used to retrieve the cloud effective particle size and optical depth from VIIRS visible and near-infrared reflectances.