Operational application and evaluation of the quantitative precipitation estimates algorithm based on the multi-radar mosaic

The real-time system of QPE (Quantitative Precipitation Estimates) together with the real-time evaluation based on the multi-radar mosaic has been successfully implemented in the operation at the Weather Bureau of Hangzhou in Zhejiang Province. A comprehensive evaluation is presented in this paper and meanwhile the error sources are analyzed according to the characteristics of vertical profile of radar reflectivity using the four different precipitation events. The system unites the basic data from the six CINRAD (China New Generation of Weather Radar) at Hangzhou, Ningbo, Zhoushan, Jinhua and Quzhou and the gauge data within Zhejiang Province which are quality-controlled in real time by the IDW (Inverse Distance Weights) method, and in order to reduce systematic and local errors, both the dynamic Z-R relationship and optimal interpolation method are integrated into the system to calibrate the QPE field. From the verification and analysis of the four events, some conclusions are as follows: (1) In northwestern and the southwestern Zhejiang, if the reflectivity sources from the bright-band (the top of the cloud), it results in the overestimation (underestimation) of radar QPE of the stratiform rainfall system. (2) In the case of the coexistence of different rainfall types the use of relative uniform Z-R relationship will result in serious local overestimation and underestimation of QPE during the Meiyu front/typhoon. (3) The severe convection with the squall line and the asymmetry of typhoon are important reasons of the error in the radar QPE. And, (4) although the combination of the Z-R relationship with the optimal interpolation can effectively reduce the systematic error, some large local error remains in the QPE.