Effects of a gamma DSD with variable shape parameter on polarimetric radar moments

Recently, the assimilation of polarimetric information emerged as a new and promising research field to achieve a better representation of cloud and precipitation processes in NWP and in this context the capability of drop size distribution (DSD) parameterizations to produce physically reliable polarimetric moments is a mandatory prerequisite. We study parameterizations of the gamma DSD used in numerical weather prediction (NWP) and their effects on polarimetric radar variables. We derive DSD parameters based on the models of Seifert [12] and Milbrandt and Yau [7] and apply a T-matrix code to obtain synthetic polarimetric radar variables. We find an untypical behavior in Z
_DR
which occurs when using the DSD parameterization [12].