中国大陆地区小时极端降水阈值的计算与分析

文章概述了近10 a来关于中国极端小时降水的研究成果，为及时了解和掌握该领域研究进展、开展相关科学研究和进行强降水预报服务提供有价值的科学依据和参考。现有的研究表明：（1）极端小时降水的阈值通常采用百分位和拟合经验函数得到，阈值强度分布在中国的区域差异大，最强阈值位于华南沿海、海南岛、台湾岛和华北平原，次大值位于四川盆地和长江中下游地区。（2）根据中国极端小时降水发生的天气背景特征，主要分为四大类型：热带气旋型、锋面型、低涡或切变线型、弱天气尺度强迫型。每种类型极端小时降水的空间分布、季节变化和日变化特征各不相同。（3）定义“极端小时降水事件”为：站点连续观测到降水大于等于0.1 mm·h^-1的一段时间，其中最多只有1 h的降水间断，且至少发生一次极端小时降水。中国极端小时降水事件维持时间在东南沿海、长江中下游一带较长（超过12 h），而在中国北方则普遍较短（不到6 h）。极端小时降水事件具有不对称性，即从降水开始到出现雨量峰值较为迅速，而从出现峰值至降水结束则变化较为缓慢，该特征在西部地形复杂地区更为明显。（4）过去50多年，中国极端小时降水的变化趋势呈现正负相间的空间分布特征。观测分析表明，上海和珠三角城市地区极端小时降水在城市化迅速发展的近30 a间具有区别于周围地区的显著增长趋势，而观测和模拟均表明北京城市强热岛效应有利于增强小时降水。

Evaluation of the convection-resolving regional climate modeling approach in decade-long simulations

This paper summarizes the research progress on extreme hourly precipitation (EXHP) over China in the past decade. The main results are as follows. (1) Thresholds of EXHP are usually defined using the percentile method or the empirical distribution function method. The thresholds of EXHP in China show substantial regional variations, with the most intense centers over the coastal South China, Hainan and Taiwan islands, and North China Plain, and two secondary ones in the Sichuan Basin and the middle-lower-reaches of the Yangtze River. (2) The EXHP records are classified into four types according to the synoptic situations under which they occur, i.e., the tropical cyclone, surface front, low-level vortex/shear line, and weak-synoptic forcing types. Each type presents distinctive characteristics in regional distribution and seasonal or diurnal variations. (3) An extreme hourly rainfall event (EXRE) is defined as a continuous time period with hourly rainfall rates at a station ≥ 0.1 mm·h^-1, with at least one EXHP record and at most 1 h intermittence. The average duration of EXREs exceeds 12 h in the southeast coastal regions and the Yangtze River valley, but is relatively short (< 6 h) in northern China. The rainfall evolution of EXREs is asymmetric, i.e., rainfall rates increase rapidly from the beginning of an event to the extreme value, but more slowly afterwards to the end of the event, especially over the complex terrains in western China. (4) Over the past 50 years, the positive trends of EXHP in China are scattered. Significant increasing trends of EXHP are observed in Shanghai megacity and the urban cluster over the Pearl River Delta during the rapid urbanization period, which differ from their surrounding areas. Both the observation and modeling studies suggest that the strong urban heat island effect in Beijing is conductive to intensification of hourly precipitation.