Radar-based hail detection

Damaging hailstorms are rare but are significant meteorological phenomena from the point of view of economic losses in central Europe. Because of the high spatial and temporal variability of hail, the proper detection of hail occurrences is almost impossible using ground station reports alone. An alternate approach uses information from weather radars. Several algorithms that use single-polarisation radar data have been developed for hail detection. In the present study, seven algorithms were tested on well documented recent hail events from Czechia and southwest Germany from 2002 to 2011. The study aimed to find the optimal threshold values for the applications of these techniques over the Czech territory and for evaluating the climatology of hail events. The results showed that the Waldvogel technique and the NEXRAD severe hail algorithm were the most accurate methods for hail detection over the area of interest. A combined criterion was proposed based on a combination of previously tested techniques. The precision of this “combi-criterion” was demonstrated for a severe hail event. The abilities of the tested criteria to provide information about a hail-fall area distribution and hail damage risk over the Czech territory were shown and discussed.