Variation Trend of Precipitation in the Pearl River Basin in Recent 50 Years

Influenced by intensifying human activities and constant changes of global climate, hydrological factors of the Pearl River Basin have been changed significantly. By using the Mann-Kendall trend test method and the sequential cluster analysis, this paper systematically analyzed the trends and mutation of the 16 precipitation indices in the Pearl River Basin. Results indicate that: 1) In the Pearl River Basin, the annual total precipitation, the total precipitations in spring and winter increase faintly, while the precipitation amount in autumn shows a stable decreasing trend. Besides, the precipitation amount in summer does not indicate a significant changing tendency. Meanwhile, the trends of precipitation amount in summer have the greatest impacts on the spatial distribution of the annual total precipitation variations. Additionally, the precipitation amount trend in spring takes the second place, which followed by the precipitation amount trends in autumn and winter. 2) There is a slight increase in the proportions of spring and winter precipitation to annual precipitation, while decreasing trends are found in the proportions of summer and autumn precipitation to annual precipitation in the Pearl River Basin. 3) In the Pearl River Basin, the total numbers of annual rainy days and light rainy days are decreasing significantly, however, the downfall days, torrential rainy days and the 95% percentile of the rainy days distributions tend to increase. Moreover, the significant tendency of light rainy days, torrential rainy days and the 95% percentile of the rainy days distributions have mutations in the early 1990s. 4) In the Pearl River Basin, the mean daily precipitation intensity is increasing stably, and precipitation period is centralizing, which can easily trigger occurrence of floods and droughts.