三江源作为“中华水塔”， 是中国重要的淡水之源和生态系统屏障。降水集中度、 季节降水量、 降水频率和降水强度的演变是气候变暖背景下水循环的关键过程， 对植被生长和水资源管理具有重要意义。本研究利用中国气象局1961 -2020年的CN05.1日降水格点数据， 计算了三江源的降水集中度指数（Precipitation Concentration Index， PCI）， 厘清了三江源降水集中度和降水年内分配的演变规律， 研究了季节降水量、 降水频率和降水强度的气候态、 年际变化、 长期趋势以及距平变化。研究结果表明： （1）三江源地区降水集中指数PCI为17.5， 降水具有一定集中性； 整个区域PCI由东南向西北递增， 降水集中度增大； 近60年三江源地区PCI以-1.71%·（10a）^-1的变化率减小， 降水的年内分配趋于均匀； 生长季降水分配的减少将影响该地区农业生产和生态系统的维持。（2）近60年不同季节降水量和降水强度整体呈现显著增加趋势， 夏季降水频率减少， 其他季节降水频率增加； 春夏秋三个季节降水强度的增加主导了降水量的增加， 冬季降水频率的增加主导了降水量的增加。冬春季增湿高于夏秋季， 春季降水量和降水强度的增长率为8.09%·（10a）^-1和6.94%·（10a）^-1， 冬季降雪量和降雪频率的增长率为7.27%·（10a）^-1和4.4%·（10a）^-1； 长江源区部分地区的旱涝分布趋于极端化， 生态系统的脆弱性加剧。（3）近60年三江源区域平均的降水量、 降水频率和降水强度以每年1.36 mm、 0.024%和0.0056 mm·d^-1的数值增加； 降水量、 降水频率和降水强度累积距平整体呈现负距平， 突变年份分别为2003年、 1989年和2003年； 雨季降水频率减小， 降水强度增加， 旱季降水频率和降水强度均增加， 这种变化在近10年尤为剧烈。本研究可以为该地区土壤侵蚀、 农业生产、 水资源管理以及气候变化相关研究提供参考。

The Three River Headwaters （TRH） region， known as the “Water Tower of China”， is a crucial freshwater source and an ecological barrier in China.Changes in precipitation concentration， seasonal precipitation amount， frequency， and intensity is a key process of water cycle in the context of global warming， holding significant implications for vegetation growth and water resource management in the TRH region.In this study， utilizing the CN05.1 daily precipitation gridded dataset from 1961 to 2020 prepared by the China Meteorological Administration， the Precipitation Concentration Index （PCI） were calculated， and the evolving patterns of precipitation concentration and intra-annual distribution in the TRH region were clarified.The climatology， relative interannual variability， long-term trends， and anomalies of annual and seasonal precipitation amount， frequency， and intensity were investigated.The results find that： （1） Precipitation in the TRH region exhibits a certain degree of concentration with PCI of 17.5.PCI increased from southeast to northwest， suggesting an increased precipitation concentration.Over the past 60 years， PCI has declined at a rate of -1.71% per decade， indicating a trend towards more evenly distributed monthly precipitation throughout the year.It’s noteworthy that the reduction in the proportion of precipitation during the growing season may have ramifications for agricultural production and ecosystem maintenance in the TRH region.（2） Over the past six decades， there has been a significant overall increase in precipitation amount and intensity during different seasons.However， precipitation frequency decreased during summer while increasing in other seasons.Enhanced precipitation intensity has predominantly contributed to the rise in precipitation amount during spring， summer， and autumn， while increased precipitation frequency has played a dominant role in elevating precipitation amount during winter.The increase rate in humidity during winter and spring was higher than that during summer and autumn.In spring， precipitation amount and intensity increased by 8.09% and 6.94% per decade respectively， while winter saw snowfall amount and frequency grow by 7.27% and 4.4% per decade.Also noteworthy is the distribution of droughts and floods in parts of the Yangtze River source area tends towards extreme， exacerbating the ecosystem vulnerability.（3） The regional average precipitation amount， frequency， and intensity in the TRH region have shown an increase of 1.36 mm， 0.024%， and 0.0056 mm·d^-1 per year over the past 60 years.The cumulative anomalies of precipitation amount， frequency， and intensity in the last 60 years were negative， with abrupt changes occurring in 2003， 1989， and 2003， respectively.There has been a significant decrease in precipitation frequency during the rainy season， coupled with a substantial increase in precipitation intensity.In contrast， both precipitation frequency and intensity during the dry season have experienced significant increases.These changes have been particularly pronounced in the past decade.This study can serve as a valuable reference for research concerning soil erosion， agricultural production， water resource management， and climate change in the TRH region.