两广地区热带气旋极端降水特征及成因初探

CHARACTERISTICS OF TROPICAL CYCLONE EXTREME PRECIPITATION AND ITS PRELIMINARY CAUSES OVER MAINLAND OF THE SOUTH CHINA

基于1960—2014年中国广东、广西地区(简称两广地区)184个台站的逐日降水资料、热带气旋(TC)最佳路径集以及ERA-Interim、ERA-40再分析资料,利用TC降水天气图客观识别法、TC路径相似面积指数、动态合成法,从TC过程最大日降水的角度,分析了两广地区TC极端降水的时空特征,并针对主要特征进行成因诊断。结果表明:50年来,两广地区TC过程的最大日降水≥50、100 mm的频数分别呈-0.66和-0.44次/(10年)的下降趋势,而最大日降水≥250 mm频数则表现出0.16次/(10年)的上升趋势;TC最大日降水频数和强度的大值区主要分布在沿海,并由沿海向内陆递减;大值区相对集中于粤东沿海(东部分区)、珠江三角洲西侧沿海(中部分区)和雷州半岛至广西沿海(西部分区)三个分区,且西部分区在TC最大日降水的平均强度及各级别频次上均为三分区之最大。对比分析发现,造成西部分区极端降水的TC路径规律性较强,主要为TC西行路径,且其登陆点集中在西部分区;对TC极端降水成因分析表明,TC移动速度慢和南海夏季风强度增强均有利于极端降水产生。

Based on 184 meteorological-station daily precipitation data during 1960-2014 over mainland of the South China（Guangdong and Guangxi）, Tropical Cyclone（TC） Best Track Dataset, ERA-interim Reanalysis Dataset and ERA-40 Reanalysis Dataset, and applying the Objective Synoptic Analysis Technique（OSAT）, tropical cyclone track similarity area index（TSAI） and the dynamic composite analysis, analyses were carried out on characteristics of TC extreme precipitation and its preliminary causes from a perspective of TC maximum daily precipitation （TMP）. Results display thai, during the past 50 years, regional-mean frequencies of TMPs above 50 mm, 100 mm and 250 mm show -0.66 times/（10 y） and -0.44 times/（10 y） decreasing trends and 0.16 times/（10 y） increasing trend with obvious interannual variations, respectively. Frequencies and intensities of different level TMPs present a similar distribution pattern of large values distributing mainly along the coastal regions and decreasing quickly from coastal regions to inland regions. In addition, large values concentrate in three subregions： the eastern coast of Guangdong （the eastern subregion）, the western coast of the Pearl River Delta （the middle subregion） and the coast from the Leizhou Peninsula to coast of Guangxi （the western subregion）, with the western subregion being the one with largest values of intensity and frequency. Comparison analysis reveals that, the TCs, which cause extreme precipitation in the western subregion, have tracks of the strongest regularity with mainly westward movement and landfall locations concentrating within the area. Meanwhile, causes analysis preliminarily reveals that TC＇s slow movement and reinforcement of the South China Sea Summer Monsoon are in favor of producing extreme precipitation.