江淮梅雨对东亚副热带夏季风进程及海温异常的响应

利用1960—2020年江淮地区75个气象站逐日降水量、气温、相对湿度资料以及NCEP/NCAR再分析资料和Hadley中心海表温度资料，研究了东亚副热带夏季风进程变异对江淮梅雨的影响，揭示了不同类型梅雨期太平洋海温及大气环流异常特征。结果表明：8种江淮梅雨类型中，多雨型占45.9%，少雨型占54.1%，其中多雨型在前30 a占36.7%，后31 a占63.3%。江淮典型梅雨年（高温高湿多雨）的主要特征为安徽南部、江苏中部及湖北东部地区降水偏多，安徽南部、江西东北部及浙江西北部气温偏高，淮河流域湿度大；而在非典型梅雨年（低温低湿少雨）大部分地区雨量偏少，气温呈"东高西低"分布，低温中心区位于淮河中游，湿度呈"西大东小"分布。欧亚大陆中高纬度阻塞高压增强，脊前向南输送的西北气流加强且路径偏东，中国东北冷涡强度较强且位置偏西南，东亚大槽加深，槽后冷空气向南输送，有利于典型梅雨形成。当前期冬春季赤道东太平洋海温异常偏高，西太平洋海温异常偏低时，西太平洋副热带高压强度偏强、面积偏大、脊线位置偏南、西伸脊点偏西，东亚副热带夏季风推进到江淮地区的时间偏早，出梅偏晚，梅雨期降水量偏多。

Response of Meiyu in Jianghuai region on the process of East Asian subtropical summer monsoon and sea surface temperature anomaly

According to the Meiyu monitoring indices, by using the daily precipitation, air temperature, relative humidity data of 75 meteorological stations in Jianghuai region from 1960 to 2020, the NCEP/NCAR reanalysis data and Hadley central SST (Sea Surface Temperature) data, the influence of East Asian subtropical summer monsoon variation on Meiyu was studied, and the anomalous characteristics of Pacific SST and atmospheric circulation during different types (typical and atypical) of Meiyu periods were revealed. The results show that among the eight types of Jianghuai Meiyu, the rainy type accounts for 45.9%, and the less rainy type accounts for 54.1%. The rainy type accounted for 36.7% in the first 30 years and 63.3% in the last 31 years. The typical Meiyu (high temperature, high humidity and rainy years) in Jianghuai is mainly more precipitation in southern Anhui, central Jiangsu and eastern Hubei, high temperature in southern Anhui, northeastern Jiangxi and northwestern Zhejiang, and high humidity in the Huaihe River Basin. However, in the atypical Meiyu (low temperature, low humidity and little rain), there is less rainfall in most areas, mainly in Jiangsu Province; the temperature is high in the east and low in the west, the central area of low temperature is located in the middle reaches of the Huaihe River, and the humidity is big in the west and small in the east. The blocking high pressure in the middle and high latitudes of Eurasia is strengthened, the northwest air flow conveying southward in front of the ridge is strengthened and the path is eastward, the cold vortex in Northeast China is strong and its position is inclined to the southwest, the East Asian trough is deepened, and the cold air behind the trough is transported to the south. It is beneficial to the formation of typical Meiyu. When the SST in the equatorial eastern Pacific is abnormally high in winter and spring, and the SST in the western Pacific is abnormally low, the intensity of the western Pacific subtropical high is stronger, the area is larger, the position of the ridge line is southward, and the westward extension of the ridge point is west. The time of the East Asian subtropical summer monsoon advancing to the Jianghuai region is earlier, the plum is late, and the precipitation is more in the Meiyu period.