Warm rainy clouds and droplet size distribution

Abstract

This paper presents the analysis of cloud droplet size distribution (DSD) and the use of a proxy variable for the parameters of the DSD to explore the possibility of detecting warm rainy clouds. Cloud DSD plays a paramount role in the parameterization of cloud microphysics in climate models. The droplet size distribution also plays a crucial role in determining the radiative properties of clouds and is usually obtained using satellite retrieval algorithms. This paper presents an analysis of the modified Gamma model which is used to represent the cloud DSD. The analysis of the DSD is conducted through the derivation of the distribution moments and their physical interpretation. The analysis includes the discussion of the mean, variance, effective radius, and effective variance of the DSD. Usually the effective radius is extracted from radiance measurements. However, since the modified Gamma distribution has two parameters it requires estimates of both the effective radius and effective variance to properly estimate cloud microphysics from radiance information.