Full Optical Simulation of Partly Cloudy Scenes

This paper discusses recent advances in the full spectral simulation of scenes with partial cloud cover. We examine the effect of broken cloud fields on the solar illumination reaching the ground. Application of aerosol retrieval techniques in the vicinity of broken clouds leads to significant over-prediction of aerosol optical depth because of the enhancement of visible illumination due to scattering of photons from clouds into clear patches. These illumination enhancement effects are simulated for a variety of broken cloud fields using the MCScene code, a high fidelity model for full optical spectrum (UV through LWIR) spectral image simulation. MCScene provides an accurate, robust, and efficient means to generate spectral scenes for algorithm validation. MCScene utilizes a Direct Simulation Monte Carlo approach for modeling 3D atmospheric radiative transfer (RT), including full treatment of molecular absorption and Rayleigh scattering, aerosol absorption and scattering, and multiple scattering and adjacency effects.