区域极端降水事件阈值计算方法比较分析

根据南京站1951—2010年逐日降水资料,采用2种传统的百分位法以及3种正态变换方法,探讨了确定区域极端降水事件阈值的最佳方法。结果表明,由于降水量的实际概率分布是一种明显的偏态分布,而传统的百分位法是在假设降水量遵从均匀分布条件下进行的,计算结果的稳定性较差。正态变换的3种方法是在降水量实际概率分布下采用百分位法计算阈值的,结果稳定性较好。其中以方法4效果最佳。为消除气候变化的影响,可以将研究时段按降水量变化的不同趋势分为几个气候阶段分别计算阈值。或者采用滑动气候阶段处理整个研究时段,并以各个滑动气候阶段阈值的平均值作为整个研究时段的阈值。

Comparative study of calculated threshold values in regional extreme precipitation

According to 1951-2010 daily precipitation data from Nanjing weather observation, the optimal threshold method of the extreme precipitation events is determined using two traditional percentile methods and three normal transformation ones. The results show that the actual probability distribution of precipitation is a skewed Gamma pattern, while the traditional percentile method complies with the assumption that precipitation is carried out under uniform conditions, whose calculated results are less stable; normalization of the three methods calculate the threshold under the actual probability distribution of rainfall by percentile method, whose result is of better stability, and of which the best method is method 4; to eliminate the effects of climate change, threshold value can be calculated by dividing researching periods into several different climate phases in terms of different trends in precipitation change, or threshold throughout the study period is equal to average value of each sliding climate stage threshold by using sliding stage to deal with the whole study period.