The Variation Characteristics Of The Precipitation And Its Cause Analysis In Yangtze River Delta

Based on the daily precipitation data from 33 weather stations in the Yangtze River Delta from 1960 to 2013, the grid data of NCEP/NCAR, the subtropical high index data and global sea surface temperature (SST) data, and trend analysis, wavelet analysis, methods of M-K, correlation analysis and methods of EOF are also employed, this article aims to analyze the characteristics of spatial and temporal distributions and variations of the precipitation in the Yangtze River Delta.The results show that:(1) Annual precipitation of Yangtze River Delta has a slight increasing trend. Decreasing in the number of light rainy days lead to significant reduction in annual precipitation days, precipitation and days of heavy rain and rainstorm have a rising trend. Different precipitation levels of annual precipitation intensity show an increasing trend, especially light rain and rainstorm. Extreme precipitation mainly concentrated on May to September, extreme precipitation index are on the rise. (2) There is a positive relationship between PCD, PCP and precipitation over the Yangtze River Delta.In the temporal of precipitation, PCD and PCP display increasing trend. The Interannual and decadal variation of PCD and PCP have the similar period oscillation with precipitation. There is obvious cyclonic convergence and abundant moisture transport near the Yangtze River Delta in the higher PCD years. The result will be opposite in the lower PCD years. (3) In partial precipitation years, Yangtze River Delta in a flat westerly flow with strongly convection, and there is southerly airflow provided water vapor. At 500hPa Eurasian is "+-+" wave pattern form east to west and Eastern East Asia is "-+-" wave pattern form south to north. The result will be opposite in partial precipitation teenager. (4) There is a good positive correlation between precipitation and the intensity and ridge line of subtropical high index, and a negative correlation with the subtropical high ridge. The sea surface temperature anomaly (SSTA) of the coast of Peru, eastern Australia waters and southern waters of Cape of Good Hope over Atlantic and India ocean sustained high (low) is the obvious signal of precipitation more (less) in Yangtze River Delta.This article believes that, the different atmospheric circulation background, differences in water vapor transport and changes in the intensity and location of WPSH are important factors affecting precipitation in the Yangtze River Delta, parts of the ocean sea surface temperature anomalies corresponding precipitation anomalies on the Yangtze River Delta.