Statistical Characteristic Of Summer Extreme Rainfall And Its Relation With Large-Scale Climate Change Over Eastern China

Based on the daily rainfall data from 1961 to 2012,429 stations with no missing chosen from May to September over Eastern China are introduced to the Generalized Pareto Distribution (GPD) to study the spatial distribution of extreme rainfall statistical characteristic in 52 years, as well as in different periods of El Nino-Southern Oscillation(ENSO) and the Pacific decadal oscillation(PDO). The causes are also discussed through the composite fields of 850hpa wind and 500hpa height anomalies. So we can get pilot studies of the influence of ENSO and PDO, which on behalf of interannual and decadal large-scale climate change, on extreme rainfall. The results show that:(1) The thresholds decrease from southeast to northwest, and the trends of thresholds are basically positive over Eastern China. There are high probabilities of maximum rainfall in South China for there are largest values of scale parameter. And the probabilities of maximum rainfall are increasing to the south of the Yellow River. The largest values of return level are in the south of Guangdong and Guangxi. And the trends are basically negative in the north, while positive in the south. Altitude will affect the return level of extreme rainfall, while the higher the altitude is, the more extreme rainfall it will be.(2) In the summer of El Nino developing years, there is cyclone circulation anomaly in the western Pacific. And the Southeast China is under the influence of north wind anomaly on the west of the cyclone, which leads to less rainfall in most places over Eastern China. The scale parameter is large in central Shanxi, bonder region of Jiangsu and Shandong and bonder region of Hunan and Guangxi. There have more probabilities of record-breaking maximum rainfall only in coastal Fujian, the junction of Hunan and Guangxi, north Henan and west Heilongjiang. In El Nino decaying years, there is more rainfall. The scale parameter is large in Mideast Neimenggu, bonder of Shanxi and Gansu and south Jiangxi to west Guangdong. The probability of severe flooding disaster is large in east central Guangdong and at the junction of Hunan, Hubei, and Jiangxi. In La Nina developing years, there is anticyclone circulation anomaly in the western Pacific. The south wind anomaly on the west of the anticyclone leads to more extreme rainfall. There are more probabilities of flood in the junction of Hunan, Hubei, and Jiangxi and north Jiangxi. But it is opposite in La Nina decaying years.(3)In the summer of cold phase of PDO, the rain band is in the north than usual. There is more rainfall in North China. And the western Pacific subtropical high is weak, which leads to less rain in central China, includes Jianghuai region. The scale parameter is larger in the Southeast than usual. In warm phase of PDO, the rain band is in the south than usual. There is more rainfall in Yangtze River Basin. The scale parameter is larger in south Jiangsu, Zhejiang, Anhui, south Jiangxi and east Guangdong. But it is opposite in other places. And there are more probabilities of flood in the lower reaches of Yangtze River Basin.