Generated using V3.0 of the official AMS LATEX template–journal page layout FOR AUTHOR USE ONLY, NOT FOR SUBMISSION! A comparison between four different retrieval methods for ice-cloud properties using data from the CloudSat, CALIPSO, and MODIS satellites

The A-Train constellation of satellites provides a new capability to measure vertical cloud profiles leading to more detailed information on ice-cloud microphysical properties than has been possible up to now. A variational radar-lidar ice-cloud retrieval algorithm, VarCloud, takes advantage of the complementary nature of the CloudSat radar and CALIPSO lidar to provide a seamless retrieval of ice water content, effective radius and extinction coefficient from the thinnest cirrus (seen only by the lidar) to the thickest ice cloud (penetrated only by the radar). In this paper, several versions of the VarCloud retrieval are compared with the CloudSat standard ice-only retrieval of ice water content, two empirical formulas that derive ice water content from radar reflectivity and temperature, and retrievals of vertically integrated properties from the MODIS radiometer. Typically the retrieved variables agree within a factor of 2, on average, and most of the differences can be explained by the different microphysical assumptions. For example, the ice water content comparison illustrates the sensitivity of the retrievals to assumed ice particle shape. If ice particles are modeled as oblate spheroids rather than spheres for radar scattering then the retrieved ice water content is reduced by on average 35 % in clouds with a reflectivity factor larger than 0 dBZ. Th