The retrieval of cloud radiative and microphysical properties using combined near-infrared and microwave radiometry

Abstract

The optical depth of a cloud is an important parameter in describing its radiative properties. Many schemes have been developed to retrieve optical depth from measurements of reflectance in the visible or near-infrared. In this paper the impact of cloud inhomogeneity and vertical structure on the retrieval of optical depth is discussed. Retrievals of cloud optical depth and effective radius using the multi-channel radiometer flown on the UK Meteorological Research Flight C130 are presented for clouds studied during the Atlantic Stratocumulus Transition Experiment. A new technique for retrieving cloud optical depth, which is less susceptible to cloud inhomogeneity, using combined microwave and near-infrared radiometry, is presented. This technique is tested for three flights both in the Azores and the South Atlantic and shows good agreement with in situ measurements. Finally the use of these retrieved parameters in radiation codes is considered.