长江上游流域降水结构时空演变特性

Spatial-temporal variability characteristics of precipitation structure across the upper Yangtze River basin,China

为研究气候变化和人类活动背景下的长江上游流域降水结构时空分布特性,利用长江上游流域67个气象站点1961—2005年45年的日降水资料,分析了各种不同历时连续降水的时空演变特征。通过Trend Free Pre-Whitening方法消除降水时间序列中的自相关成分,利用非参数的Mann-Kendall法检验了降水结构的变化趋势。结果表明:①长江上游流域及各分区各历时降水发生率随降水历时增加呈指数递减趋势,贡献率先增加后降低,以短历时降水为主;②长江上游短历时(1 d和2 d)降水贡献率发生突变的时间在1976年,长历时(6 d和10 d)降水发生率发生突变的时间为1984年,贡献率发生突变的时间为1999年;③长江上游短历时降水集中出现的次数增加,降水强度增大,降水量占总降水量的比例较大,而长历时降水出现频次降低,降水量占总降水量比例下降,其中岷沱江流域、大渡河流域、长江干流区间通过了显著性检验。

Daily precipitation data covering 1961--2005 from 67 meteorological stations across the upper Yangtze River basin are used to analyze spatial-temporal variability characteristics of precipitation structure in the context of climate change and human activities. The autocorrelation component in precipitation time series is eliminated by the Trend Free Pre-Whitening method, while the variability and trend in the precipitation structure are detected by the nonparametric Mann-Kendall method. Results show that over the upper Yangtze River basin and its sub-basins, the in- cidence rate of precipitation events for different durations decreases exponentially with the increase of precipitation du- rations; while, the corresponding contribution rate is found to be first increasing and then decreasing, with predominantly by short-duration precipitation events. It is detected that the year of 1976 was marked by an abrupt change for the contribution rate of short-duration （ 1 d and 2 d） precipitation events ; while, the timing of abrupt changes for incidence rate and contribution rate of the precipitation events with long-durations of 6 and 10 days was in 1984 and in 1999 respectively. An upward trend is detected in the number of consecutive occurrences of short-duration precipitation events, with higher precipitation intensity and contributing to larger portion of total precipitation amount ; while, the opposite is true for long-duration precipitation events. Tests are all significant for both above characteristics of precipitation structure amongst the Min River basin and the Dadu River basin, which are the sub-basins of the upper Yangtze River basin, as well as its main course areas.