Operational application of combined radar and raingauges precipitation estimation at the CHMI

Abstract

The Czech Hydrometeorological Institute (CHMI) runs two C-band Doppler weather radars which provide good coverage of precipitation over the area of the Czech Repub- lic. For the quantitative precipitation estimation (QPE), re- flectivity from pseudoCAPPI level of 2 km above sea level is used and the rainfall rate is then obtained by a constant Z-R relationship. Since the radar-only-based QPE is not consid- ered satisfactory, some corrections have been introduced in order to achieve better accuracy of the instant precipitation estimates. The corrections include the algorithm using verti- cal profile of reflectivity which reduces the range-dependent underestimation of single radar estimates, raingauge-based adjustment and combination with available raingauge mea- surements. The adjustment using single coefficient over the radar domains is based on collocated radar and raingauge measurements in a time-moving window whose length is an adaptable parameter. The combination of the adjusted radar QPE with available raingauge measurements is achieved by a simplified method of double optimal estimation. The sys- tem is in routine operation for precipitation accumulation of 1, 6 and 24 h and the results are available in HTML format. It serves for warning purposes, for NWP model verification and hydrological applications at the CHMI. The visualiza- tion allows for quick comparison of radar, radar-adjusted, raingauge-only and combined estimates along with mean areal QPE for predefined catchments using all mentioned es- timates. The instant comparisons and some additional diag- nostic information allows to see better the deficiencies and errors of the two complementary estimation systems.