Relating radiance and irradiance: Using 2D cirrus cloud fields from remote sensing for a model-measurement comparison of spectral irradiance

During the Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment (CRYSTAL-FACE), the MODIS airborne simulator (MAS) and the Solar Spectral Flux Radiometer (SSFR) operated on the same aircraft. While MAS provided 2D fields of cloud optical thickness and effective ice crystal radius, the SSFR measured spectral irradiance in the visible to near-infrared wavelength range (0.3-1.7 microns). The MAS retrievals, along with vertical profiles from a combined Radar/Lidar system on board the same aircraft were used to construct 3D clouds, which were then input into a 3D Monte Carlo radiative transfer model. In this way, the modeled field of irradiances could directly be validated against the SSFR measurements. For two cases, the need of using the scattering phase function versus approximations, and the effects of cloud heterogeneities on radiative quantities are examined.