Long-term trends in summer precipitation totals, the number of rainy days, and precipitation intensity were investigated with daily rainfall datasets for China from 1961 to 2000. Total precipitation significantly increased in summer in the Yangtze River basin and northwestern China, while total precipitation decreased in other regions. The number of rainy days increased in the Yangtze River basin, and over northwestern China. In contrast, the number of rainy days decreased over Tibet and over northern and northeastern China. Seasonal mean precipitation intensity became large at most of the stations in China.
To investigate trends in heavy rainfall, daily rainfall totals during the whole investigation period were grouped into ten classes, with class width equal to l0% of total number of rainy days from 1961 to 2000, and the number of rainy days, and summer mean rainfall amount for each class, were obtained for each summer. A simple linear fit was made to determine the linear trends in the 10-class precipitation time series. The upper 20 percentile of daily precipitation totals showed a statistically significant increase over the Yangtze River basin, and over northwestern China during the study period. Class average precipitation decreased in almost 10 classes over Tibet and north and northeastern China.