The Ice Cloud Radiative Effect Estimated with Retrieved Ice Particle Roughness Based on MISR and MODIS Measurements

Ice clouds play an important role in modulating the Earth’s radiation budget, but the magnitude of their influence remains largely uncertain. Because ice cloud radiative effect is sensitive to ice cloud particle shape, using retrieved ice particle shape to compute cloud radiative effect is an ideal setting. However, ice particle shape is usually pre-defined in radiative transfer calculation due to difficulties in retrieving ice particle shape at the pixel level. The Multi-angle Imaging SpectroRadiometer (MISR) sensor measures cloud radiances at a wide range of scattering angle, offering unprecedented opportunity to retrieve ice particle shape on the pixel scale. In this presentation, we consider the degree of ice particle surface roughness in defining ice particle morphology, and retrieve the optimal degree of ice particle surface roughness in each given pixel at 1.1 km resolution using MISR dataset in a band centered at 0.86 μm. The ice particle model defined by inferred optimal surface roughness is used in radiative transfer calculation. Furthermore, the impact of the retrieved particle roughness on ice cloud radiative effect is investigated.