1960—2017年太湖流域不同等级降水时空特征

基于太湖流域1960—2017年逐日降水数据，运用Mann-Kendall非参数检验法、R/S分析等方法，分析太湖流域不同等级降水的时空变化特征，并探讨了不同等级降水对年降水的影响。结果表明：1）近60年来，流域小雨发生率最高，为73.55%；年总降水量中，中雨量所占比例最大，为32.05%。小雨发生率呈显著减少趋势，暴雨贡献率呈显著增加趋势。2）太湖流域大雨、暴雨的降水量和降水日数都呈显著增加，小雨日数显著减少，小雨强度、年总降水强度显著增强。3）不同等级降水变化趋势的空间分布存在明显差异。小雨日数与年总降水日数，以及小雨强度与年总降水强度的变化趋势空间格局相一致。中雨日数、大雨日数、暴雨日数变化趋势的空间分布与其对应的降水量变化趋势的空间格局相似。4）R/S分析结果显示，小雨、暴雨、年总降水相关指标（小雨量除外）都表现出较强的持续性，未来变化趋势与过去相一致。5）近60年来，太湖流域年总降水量、降水日数、年总降水强度的变化，分别受中雨量、小雨日数、暴雨量的影响较大。在旱年流域年降水量偏少受大雨量减少的影响较大，而涝年年降水量偏多受暴雨增加的影响较大。

(a. State Key Laboratory of Earth Surface Processes and Resource Ecology; b. Faculty of Geographical Science,Beijing Normal University,Beijing 100875, China)

Against the backdrop of global warming, the structure and patterns of precipitation have changed significantly. This includes changes in the non-uniformity of spatial and temporal distribution of precipitation, while the frequency of extreme precipitation events has increased. Studies have shown that regional drought and flood disasters are related to rainfall and also closely related to the frequency and intensity of precipitation. As the main climate factor, the spatial and temporal variation in precipitation for different grades has become of significant research interest in recent years. Based on daily precipitation data from 1960 to 2017, this study used the Mann-Kendall non-parametric test and R/S analysis (rescaled range analysis) to analyze characteristics of spatial-temporal variation for precipitation at different grades in the Taihu Lake Basin for the past 60 years. Additionally, these results were used to explore the impacts of this variation on the annual precipitation. The observed daily precipitation (P) was categorized into four grades of intensity: light precipitation (0.1≤P<10 mm/d); moderate precipitation (10 ≤P<25 mm/d); heavy precipitation (25≤ P<50 mm/d); and storm precipitation (P≥ 50 mm/d). These classification criteria have been used in many global precipitation analyses. The results show that the annual precipitation days were dominated by light rain days, accounting for 73.55% of the total annual precipitation days between 1960 and 2017. The contribution rate of light rainy days to the total annual precipitation days had significantly reduced, and the contribution rate of heavy rainfall to the total annual rainfall had significantly increased. There was a significant increase in the rainfall, rainy days of heavy and storm rain, rainfall intensities for light rain, and the annual average precipitation. The number of light rain days had decreased significantly, and the precipitation structure in the Taihu Lake basin showed a tendency to shift to extreme heavy precipitation. There were significant differences in the spatial distribution of precipitation trends for different grades. The light rainy days, total annual precipitation days, and intensities of light rain and annual average precipitation showed a similar spatial pattern in the changing trend. The light rainy days and total annual precipitation days showed a significant downward trend across the entire basin, while the intensities of light rain and annual average precipitation showed a significant increasing trend. The spatial distribution of the change in the days of moderate rain, heavy rain, and storm rain were similar to the corresponding spatial pattern of rainfall. R/S analysis showed that, in addition to light rainfall, the indicators related to light rain, heavy rain, and annual total precipitation showed strong persistence, and the future trend was consistent with that of the past. In the past 60 years, the annual total rainfall, precipitation days, and annual average precipitation intensity in the Taihu Lake basin were greatly affected by moderate rainfall, light rain days, and heavy rainfall, respectively. The annual precipitation reduction was greatly affected by the decrease in heavy rainfall in dry years, and the increase in annual precipitation was heavily impacted by the increase in storm rainfall in flood years. There is a need for further study on the climate dynamic mechanisms underpinning different precipitation grades, such as atmospheric circulation and water vapor transport.