Abstract: According to daily rainfall data at 743 meteorological stations from 1971 to 2010, we classified annual rainfall amount and rainfall days by grade and further discussed the variation characteristics of rainfall amount and rainfall days and the temporal evolution of annual rainfall in four regions (arid region, semi-arid region, semi-humid region and humid region) via linear trend analysis, accumulative anomaly, M-K test and moving-t test. Results demonstrated that (1) in the past four decades, the annual rainfall days differed among the four regions, among which the humid area experienced more days of rainfall in the middle but less in the surroundings. (2) In the north part of arid region, light rainfall contributed more with high frequency, whereas in semi-arid regions, heavy rain and rainstorm contributed less with lower frequency. (3) In terms of interdecadal change, the annual rainfall amount during 1991-2000 increased most remarkably in humid region, yet not obviously in 2001-2010 in semi-humid region. (4) The trend of abrupt change of rainfall amount was inconsistent between wet and dry regions: in humid region the rainfall amount declined abruptly in 2002, while in semi-arid region no abrupt change happened.

Key words: rainfall amount, rainfall days, wet and dry partitions, spatial distribution, temporal evolvement