基于IMERG卫星遥感数据的华南地区近20年汛期强降雨气候特征分析

利用20年(2001—2020年)多卫星联合反演的IMERG降水资料，分析华南地区强降雨区域气候差异，对比了南海夏季风爆发前的前汛期、夏季风爆发时期和后汛期三个阶段强降雨的时空分布特征和极端强降雨的日变化。结果表明：(1)华南地区多雨中心由不同时期的天气系统造成，前后汛期占全年雨量比值呈反相分布，两广沿岸暴雨占比明显高于其他区域，强降雨是华南地区多雨中心雨量的主要贡献。(2)广东近海强降雨有6月和8月双峰现象，海南强降雨单峰值在10月，两广其他区域的6月单峰态势与南海夏季风爆发密不可分。偏强夏季风在夏季风爆发时期只对两广沿岸Ⅰ区（北部湾）、Ⅱ区（阳江附近）和Ⅲ区（珠江三角洲）强降雨起到增幅作用，而在后汛期有利于整个两广沿岸和海南强降雨增多。6月上旬广东沿岸Ⅲ区和Ⅳ区（汕尾及其以东）是西南夏季风导致暖区暴雨的高频时期和多发地带。(3)海南强降雨在华南地区属极端性最高，并以午后时段极端强降雨为主，广东次之，广西最低。极端强降雨日变化又以两广沿岸晨雨特点最为突出，尤其凌晨至上午(5—11时)为Ⅱ区和Ⅲ区高发时段；广东内陆仅在夏季风爆发时期存在傍晚高峰时段。

An Analysis of IMERG Precipitation Data from 2001 to 2020

This study analyzed the regional climate variations in heavy rainfall across South China by using the IMERG precipitation data during 2001—2020.The research focused on the spatiotemporal distribution characteristics of heavy rainfall and the diurnal variations of extreme heavy rainfall before , during ,and after the onset of the South China Sea summer monsoon .The results showed that :(1)The rainfall center in South China was influenced by diverse weather systems at different times of the year . The ratios of rainfall during the two rainy seasons to the annual precipitation were inversely distributed , and the proportion of heavy rainfall along the coast of Guangdong and Guangxi was significantly higher than those of other regions .Heavy rainfall contributed the most to the overall precipitation in the rainfall center of South China .(2)The coastal areas of Guangdong experienced two peaks of heavy rainfall in June and August ,while Hainan Island observed a single peak in October .Other regions of Guangdong and Guangxi exhibited a single peak in June ,which was closely related to the onset of the South China Sea summer monsoon .During the onset of the summer monsoon ,the strong summer monsoon intensified the heavy rainfall in Zone I (Beibu Gulf ),Zone II (area near Yangjiang ),and Zone III (Pearl River Delta ) along the coastal land areas of Guangdong and Guangxi .In the second rainy season ,the summer monsoon continued to contribute to increased heavy rainfall across the entire coastal area and Hainan Island .In early June,Zone III and Zone IV (Shanwei and its eastern region )experienced a high frequency of heavy rainfall ,primarily due to warm-sector heavy rainfall induced by the southwest summer monsoon .(3) Hainan Island exhibited the highest occurrence of extreme heavy rainfall in South China ,predominantly in the afternoon .Guangdong followed with a lower occurrence ,while Guangxi experienced the lowest occurrence .The diurnal variation of extreme heavy rainfall was most pronounced in the morning along the coastal area of Guangdong and Guangxi ,especially from early morning to forenoon (5—11am),which corresponded to the peak period in Zone II and Zone III .Inland areas of Guangdong only exhibited a peak period in the evening during the onset of summer monsoon .