Analysis on the climatic characteristics of precipitation in rainy season in the Two-lake Region

Based on China' s 740 daily meteorological precipitation records, precipitation characteristics in rainy season in the Two-lake region have been analyzed by using several statistical methods. Results are as follows. (1) The yearly rain time series may be technically splitted into 5 stages, among which, the prime stage (called it Two-lake rainy season) starts at the second Hou (a 5-day period) of April and ends at the first Hou of July. The Two-lake rainy season, which comes earlier and stays longer, when compared to China' s Meiyu rainy season. (2) The first two modes of EOF, one with two intensive rainy periods (IRP2) and another with three (IRP3), are the most important modes and frequently appear in rainy season. The IRP2 mode, one intensive rainy period being in early to mid May and the other in mid to late June, had been significant during 1960s and 1990s, while the IRP3 mode, the intensive periods being in mid April, mid to late May to early June, and late June to early July, respectively, had been significant during the late 1960s to early 1970s, as well as the mid to late 1980s. (3) The quasi two-week (10-20 days) and 30-60-day oscillations are remarkable in the Two-lake rainy season. The former includes 5 complete waves and the latter includes 3 with peaks at early April, early May and mid June, being well corresponded to its first EOF' s mode.