Retrieving Optical Depths and Lidar Ratios for Transparent Layers Above Opaque Water Clouds From CALIPSO Lidar Measurements

For measurements that are made by the CALIPSO lidar, the layer-integrated attenuated backscatter of opaque water clouds gamma´_water,O can be accurately estimated for those cases for which there is no overlying aerosol or cloud layer. When transparent overlying layers of clouds or aerosols are present, the layer-integrated attenuated backscatter that is measured for the water cloud is reduced by a factor that is equal to the two-way transmittance of the upper layer. Because the layer-integrated depolarization ratio can be used to obtain an independent estimate of gamma´_water,O, we can subsequently derive both the optical depth and an estimate of the layer-averaged lidar ratio of the overlying layer.