1981—2018年甘肃省极端暴雨天气过程的气候与环流特征

Climate and Circulation Characteristics of Extreme Rainstorm Processes in Gansu from 1981 to 2018

利用甘肃省1981—2018年81个国家气象观测站逐小时降水资料和NCEP再分析资料,重点分析甘肃省不同落区极端暴雨天气过程的气候与环流特征。结果表明:(1)甘肃极端暴雨天气过程主要发生在河东地区的陇南、天水、平凉、庆阳一带,强降水中心集中在陇南的康县、徽县;按照降水落区,可划分为陇东型、陇南型、陇东南型和分散型4类。(2)甘肃7—8月最易出现极端暴雨天气,8月中旬最多,陇南出现时间早于陇东,且暴雨的夜雨特征和对流性特征较为显著,陇南和陇东南暴雨的夜雨特征较陇东更为明显。(3)近38 a甘肃极端暴雨过程存在2.5、5、10 a尺度的周期,其中2.5 a的周期振荡最明显。(4)甘肃极端暴雨天气与副高密切相关,暴雨落区与副高位置关系显著,陇东型还与北部高压脊底部的偏东气流有关,分散型还与南海的热带低压有关,陇南型和陇东南型还取决于高原短波槽的强度及位置。

Based on the hourly precipitation data at 81 national meteorological observation stations of Gansu Province from 1981 to 2018 and NCEP reanalysis data,the climate and circulation characteristics of extreme rainstorms were emphatically analyzed in different falling areas of Gansu Province.The results are as follows:(1)The extreme rainstorm weathers occurred mainly in Longnan,Tianshui,Pingliang and Qingyang of eastern Gansu,and the heavy rainfall centers concentrated in Kangxian and Huixian of Longnan.The extreme rainstorms were classified into four types including eastern Gansu,southern Gansu,southeastern Gansu and dispersion patterns,according to the falling areas of rainstorms.(2)The extreme rainstorms were easily to occur in July and August in Gansu,especially in mid-August.The extreme rainstorms in southern Gansu were earlier than in eastern Gansu.The precipitation of extreme rainstorms at night was more than in the daytime as a whole,the night rain characteristic was remarkable in Gansu,especially in southern Gansu and southeastern Gansu.In additional,the convective characteristic was significant in Gansu.(3)There were 2.5,5 and 10 years period of extreme rainstorms in Gansu during 1981-2018,and the 2.5-year periodic oscillation was obvious.(4)The extreme rainstorms in Gansu were correlated with the subtropical high,and the falling area of rainstorm was significantly related to the location of subtropical high.Moreover,the extreme rainstorms in eastern Gansu were also related to the easterly airflow at the bottom of northern high ridge,the extreme rainstorms with dispersion pattern were related to the tropical low pressure in South China Sea,while the extreme rainstorms in southern and southeastern Gansu depended on the intensity and location of short-wave trough in Tibet Plateau.