1981～2010年北京地区极端降水变化特征

采用北京地区20个常规气象站1981~2010年逐日降水数据,对北京地区极端降水的空间分布特征进行了分析。得到以下主要结论:1981~2010年,北京地区极端降水百分位数(第90、95和99个百分位数)阈值表现出较一致的空间分布特征,以第95个百分位数阈值计算的极端降水日数与降水阈值和降水量的分布有较大差异,极端降水量对总降水量的贡献可达30%~37%,极端降水强度分布与极端降水阈值分布相似。近30年,北京地区多数站点的极端降水量、降水日数和降水强度呈下降趋势,极端降水量以上甸子、怀柔、平谷和观象台下降较为明显,可达到40 mm(10 a)–1以上,极端降水强度以顺义、海淀、观象台、大兴和上甸子等站下降较为显著,每10 a降水强度减小趋势可达4 mm d–1,极端降水日数变化分布与极端降水量变化分布类似,极端降水强度变化与降水量和降水日数变化的分布有明显不同。

Variation Characteristics of Precipitation Extremes in Beijing during 1981-2010

Daily precipitation data of 20 national stations in Beijing area during 1981-2010 are used to study the extreme precipitation exceeding relative thresholds (upper 90th, 95th, and 99th percentiles of precipitation for local sites and given time). The results show that the relative thresholds of 90th, 95th, and 99th percentiles have a similar spatial distribution. The distribution of extreme precipitation days shows a significant difference from the precipitation amount and relative threshold calculated as the upper 95th percentile. The extreme precipitation amount can account for 30%-37% of the total precipitation amount. The distribution of extreme precipitation intensity is consistent with the extreme precipitation threshold. In the recent 30 years, the extreme precipitation amount, days, and intensity of most stations in Beijing area have shown apparent decreasing trends. In Shangdianzi, Huairou, Pingu, and Guanxiangtai stations, the decreasing trend of extreme precipitation amount is obvious, reaching a value of 40 mm (10 a)^-1. In Shunyi, Haidian, Guanxiangtai, Daxing, and Shangdianzi stations, the decreasing trend of extreme precipitation intensities is more pronounced, with precipitation intensity being as low as 4 mm d^-1 (10 a)^-1. The distribution trend of extreme precipitation amount is positively related to the precipitation frequency and that of extreme precipitation intensity is inconsistent with the precipitation amount, frequency, and patterns of distribution.