Synergetic use of polarimetric doppler radars at C- and Ka-band for retrieval of hydrometeor type and quantity

The verification of radar retrieval results like hydrometeor type, quantity, and dynamics of clouds is an essential requirement for assimilating observation data into Numerical Weather Prediction (NWP) models. Field campaigns were executed to enrich the observational data base with special aims - for instance the Convection and Orographically Induced Precipitation Study (COPS) in 2007 in south-west Germany and eastern France had planed to improve the Quantitative Precipitation Forecast (QPF) in mountainous areas. Therefore a huge amount of different observation instruments were concentrated in the region around Black Forest, Vogues and Rhine valley especially at so-called supersites. The current study focus on comparison between polarimetric C-band and vertically pointed Ka-band to retrieve profiles of hydrometeor type and quantity. Additional data from radio sounding, rain gauges, and distrometers were used to retrieve temperature profile, rain rate, and raindrop size distribution at ground.

The melting height level was used to confirm the spatial data synchronization of different radars. The predominant hydrometeor type were estimated from C-band radar by using polarimetric variables LDR and ZDR. Profiles of reflectivity differences from Ka- and C-band radar were analyzed to give a first guess of mean particle sizes as well as liquid and ice water content taking into account attenuation of radar beam. For comparisons additional simulations of radar reflectivity from C- and Ka- band by using T-matrix method were examined by assuming profiles of liquid water and ice particles. In a case study a more complex procedure was used to retrieve profiles of liquid and ice water content from measured raindrop size distribution at ground, vertical Doppler velocity from Ka-band radar and the attenuation corrected reflectivity difference from C- and Ka-band radar. To correct vertical velocity measurements from convective up- or downward motion additional data from an SODAR system were taken into account.