Improvement of Multi-Radar Quantitative Precipitation Nowcasting with Consistency Correction Method

The quality of mosaic QPE directly determines the accuracy of QPF products from nowcasting models. However, there is a common spatial discontinuity phenomenon caused by the biases of multiple radars in mosaic QPE. Consistency correction, a type of multi-radar quality control method, can be used to mitigate the spatial discontinuity of mosaic QPE, but its improving effect on QPF products should be analyzed.

For this consideration, a consistency correction method based on GPM KuPR proposed by Chu et al (2018a) was applied to the three S-band operational radars of China, and the improvement on QPE by Z-R relationship, deterministic QPF by S-SPROG (Spectral Prognosis), and ensemble QPF by STEPS (Short-Term Ensemble Prediction System) were analyzed. The results showed: 1) the raw reflectivity factors by the three operational radars over the same equidistance area were significantly different. After the consistency correction, the differences decreased to be less than 0.5 dB and the spatial discontinuity of mosaic products disappeared. 2) The precision of mosaic QPE was significantly improved after the correction, and the average RMSE of QPE decreased by 19.5%, and the TS of heavy rainfall and above rose by 44.8%. 3) The 0-1h deterministic QPF by S-SPROG, and ensemble QPF by STEPS were significantly improved after the correction. The deterministic (ensemble) TS of moderate rain and above rose by 11.9% (10.2%), and that of heavy rain and above increased by 34.2% (38.7%). 4) Furthermore, the consistency correction method contributed to precipitation velocity estimation, and decreased its RMSE by 25.0%. Clearly, the consistency correction method is significantly contributive to multi-radar mosaic QPE and precipitation nowcasting.