Regional heavy rain locations associated with anomalous convergence lines in eastern China

Spatial-temporal distribution and forecast skill of regional heavy rain (RHR) locations are important for disaster mitigation and saving lives and property. In China, daily RHR events are mainly concentrated in the eastern summer monsoon region. Daily site precipitation of 460 stations from 1960 to 2010 used in this analysis showed that there are inter-annual and decadal variability in site heavy rain (SHR) events with the yearly mean frequency of about 181 events. Maximal 218 SHR events occurred in 1983, while minimal 161 SHR events in 2004. The inter-annual and decadal variability in daily RHR events was detected from two to four adjacent stations, while a long-term increasing trend of daily RHR events was found from exceeding five adjacent stations. An approach of decomposing an atmospheric variable into a climatic field and a temporal anomaly is used to establish the relationship between daily RHR events and anomalous synoptic systems. Here, four cases and 21 case composite analyses showed that most daily RHR events are located along anomalous convergence lines and anomalous height troughs in the lower troposphere. This relationship suggested that anomaly-based synoptic chart should be applied in the practice of short-term and medium-range forecasts, by using the products of the current state-of-the-art operational numerical weather models.