Precipitation forecast evaluation by polarimetric radar

A good representation of clouds and precipitation in Numerical Weather Prediction (NWP) models is essential for an accurate direct prediction of local weather elements. In order to improve the quality of precipitation forecasts it is necessary to evaluate and better parameterise these processes determining the amount of precipitation at the ground. This has to be done through verification against observations. Polarimetric radar systems give information on the temporal and spatial distribution of hydrometeors in the atmosphere and are able, in contrast to conventional radar, to classify the hydrometeors such as rain, hail, graupel, and snow. Therefore they are especially suited for the verification of the microphysical parameterisation of high resolution models particularly in strong convective systems. In order to make the polarimetric information usable for the model verification, the polarimetric radar forward operator SynPolRad (Synthetic polarimetric Radar) has been developed using the T-Matrix Code. SynPolRad is able to reproduce the polarimetric signatures of rain as well as the ice phase hydrometeors under consideration of the bright band. These synthetic polarimetric parameters can be directly compared in the same physical units to the polarimetric radar observations. The features of SynPolRad will be discussed and applied on a case study of a convective event in southern Germany observed by the polarimetric radar Poldirad.