北京地区夏季极端降水变化特征及城市化影响

利用1981-2016年京津冀地区174个国家站逐日降水资料，采用百分位方法和线性倾向估计方法对京津冀地区极端降水的时空分布特征及演变趋势进行了分析。结果表明：（1）对于京津冀地区极端降水空间分布，不同百分位降水阈值表现为一致的分布特征，年平均极端降水量、平均极端降水强度与百分位极端降水阈值分布大体一致，而年平均极端降水日数的分布则与其相反。（2）年平均极端降水量在103.6~259.1 mm之间，年平均极端降水日数在3.0~4.0 d之间，平均极端降水强度在大雨到暴雨之间，极端降水量对总降水量贡献达28%以上。（3）极端降水总站次和极端降水日数年变化趋势一致，7月、8月和10月是极端降水较活跃月份。（4）在36 a期间，年平均极端降水量、年平均极端降水日数、平均极端降水强度以及极端降水量对总降水量贡献的变化趋势分布情况基本一致，呈减少趋势的站点均相对较多，年平均极端降水量增减幅度较大，年平均极端降水日数变化在1 d·（10 a）^-1以内，平均极端降水强度和极端降水量对总降水量贡献减少趋势相对明显。

Trends in total precipitation and frequency of daily precipitation extremes over China

Using daily precipitation data at 174 national weather stations in Beijing, Tianjin, and Hebei Province from 1981 to 2016, the spatial and temporal distributions and variations of extreme precipitation were analyzed using the percentile method and the linear tendency estimation method. The results showed that:(1) the precipitation thresholds of different percentiles showed a consistent spatial distribution. Distributions of annual extreme precipitation amount and extreme precipitation intensity were almost consistent with that of precipitation thresholds, although that for annual extreme precipitation days was opposite. (2) The annual extreme precipitation amount at each site was between 103.6~259.1 mm. The annual extreme precipitation days were about 3.0~4.0 days. The extreme precipitation intensity was between the amounts of the heavy rain and the rainstorm. The contribution of extreme precipitation to the total precipitation was above 28%. (3) The extreme precipitation sites and days showed consistent variation. Extreme precipitation was very active in July, August and October. (4) During the past thirty-six years, the variation distribution of annual extreme precipitation amounts was similar to those for the annual extreme precipitation days, intensity and contribution with more sites having exhibited declining trend. The increase and decrease of extreme precipitation amounts were large. Variation of extreme precipitation days was less than one day in ten years, and the decreasing trend of extreme precipitation intensity and contribution were significant.