The Nowcasting Method of Precipitation Based on the Maximum Overlap Rate of Radar Echo

The nowcasting method of precipitation based on the maximum overlap rate is an important part of short-term forecast radar system. On the basis of recalling the development of the radar nowcasting technology of precipitation, considering the merits of a new generation of weather radar with high spatial and temporal resolution, this paper proposes that within a short time interval, the moving direction and speed of the two adjacent radar echos with the greatest overlap rate are also the moving direction and speed of the precipitation system. The current radar echoes are translated by calculating the moving direction and speed, and are revised by use of nine-point average change amounts of echo dissipation model to form extrapolation forecasting; by use of the time weights synthesis method, the extrapolation forecasting every six minutes is synthesized to form the precipitation nowcasting field. In order to test the above-mentioned methods, the data at Hefei, Nanchang, Xiamen radar stations are used to carry out the calculation and prediction. The results show that: the moving direction and speed with the maximum overlap rate at two moments may reflect the overall movement characteristics of precipitation system, the calculation result is consistent with the subjective forecasting of forecasters and moreover it is objective, fine, and stable; using the growth and decay model to revise the translated echo can reflect the actual precipitation change; the 1-hour precipitation distribution which is synthesized by using precipitation forecasting every six minutes with the time weights synthesis method is in good agreement with the actual one.