SYSTEMATIC VARIATIONS OF Z-R-RELATIONSHIPS FROM DROP SIZE DISTRIBUTIONS MEASURED IN NORTHERN GERMANY DURING 7 YEARS

Problems and artifacts related to small samples of measured distributi ons are discussed. These ground-based samples of rain drops are small per se and extremely small compared to what the radar samples aloft. A fter indicating rules for investigating such data, preliminary analyse s and results are presented. Significant differences for all three loc ations (Hamburg, Berlin and Restock) are only found for thunderstorms, as compared to warm- or cold-air advection and weak gradient type wea ther systems. An outlook suggests a three step procedure for extractin g information from the radar image in real time, information is needed on the relationship between radar echoes aloft and precipitation at g round level in order for radar data to be used in operational hydrolog ical applications. (C) 1998 Elsevier Science B.V. All rights reserved.