Multi-Scale Analysis and Nowcasting of Short-Time Heavy Rainfall

Hourly precipitation data at 79 stations in Anhui Province during 1995 to 2009 were used to statistically compute the spatial and temporal distributions of short-time heavy rainfall with different intensity. Then the environmental background characteristics of typical short-time heavy rainfall were obtained so as to build three conceptual models of short-time heavy rainfall and abstract large-scale systems beneficial to its occurrence.By using the statistical analysis of physical parameters,conclusions can be drawn as follows. When short-time heavy rainfall occurs,the atmospheric water vapor is abundant and there are wetthick layer and warm-thick cloud layer,the latter ensures cloud particles from being evapored in the downdraft airflow of system.At the same time,moderate convective CAPE and higher KI index are beneficial for the appearance of high-efficiency precipitation.On the other hand,there are two structural characters of radar reflectivity factor,i.e.,the low-quality core structure and high-quality core structure.The important reasons for maintenance and development of heavy precipitation echo in some areas are attributed to small and mesoscale wind shear,convergence and cyclonic covergence zone.In addition,the boundary layer jet enhanced significantly half an hour before heavy rainfall is another important indicator of nowcasting of heavy rainfall.