Changes in precipitation extremes over the Pearl River Basin, southern China, during 1960–2012

Based on daily precipitation dates at 42 meteorological stations in the Pearl River Basin, the spatial and temporal changes in precipitation index are analyzed during 1960–2012, eleven indices of precipitation extremes are studied. The results show that wet day precipitation, consecutive wet days and numbers of heavy precipitation days exhibit non-significant decreasing trends in the study area. Consecutive dry days and simple daily intensity index have increased and are significant at the 95% level, while other extreme precipitation indexes have non-significant increasing trends. Spatial changes of precipitation extreme indices show obvious differences, and they are not clustered either. On the whole, the number of rainy days has decreased over the Yunnan–Guizhou Plateau and hilly Guangxi, and the spatial distribution reflects the regional climatic complexity. Continuous wavelet transform analysis indicates that there are significant periodic variations with periods of ∼7 and ∼14 years in extreme precipitation, and that there is also a 6-year period and a 14-year period with the Pacific Decadal Oscillation (PDO) and Southern Oscillation Index (SOI), respectively, which are very consistent. The PDO and SOI are important influential factors for precipitation. In addition, except for consecutive dry days, the other extreme precipitation indices have significant correlations with annual precipitation. Large scale atmospheric circulation changes derived from NCEP/NCAR reanalysis reveals that a strengthening anticyclonic circulation, increasing geopotential height, weakening monsoonal flow, and vapor transportation over the Eurasian continent have contributed to the changes in precipitation extremes in southern China.