Synergistic use of MISR and MODIS data for cloud phase and crystal habit retrievals

Knowledge of cloud phase and crystal habit is fundamentally important both for accurate remote sensing retrievals and for climate simulations. Climate model studies have shown that realistic treatment of ice crystal habit is significant to modeled climate, especially in the tropics and satellite and ground based retrievals of cloud properties depend strongly on cloud phase and habit assumptions. The shape, size, and composition of cloud particles affect the way in which they scatter light. Consequently the radiances measured by the Multi-angle Imaging Spectro-Radiometer (MISR) instrument aboard NASA's Terra satellite, which observes light scattered from the same cloud at nine different angles, are functions of the crystal phase and habit. In principle, the measured angular pattern can be used to infer the particle phase and crystal shape, however the MISR visible radiances have a lack of sensitivity to particle size. By combining the MISR multi-angular visible radiances with shortwave infrared radiances from the MODerate Resolution Imaging Spectroradiometer (MODIS) instrument also on the Terra platform, sensitivity to particle size is also incorporated, reducing ambiguity in the retrievals. Retrievals of cloud properties, including particle phase, habit, and size from MISR and MODIS radiances over the Atmospheric Radiation Measurement (ARM) sites in Oklahoma and the tropical western Pacific are presented. Sensitivities of the retrieved properties to various assumptions in the retrieval are examined. Comparisons to the operational MODIS retrievals and to ground-based radar reflectivity-velocity retrievals are performed.