ĭue to the importance of summer precipitation and Meiyu in the local area, many scholars have conducted a lot of research on their variations. For example, the Meiyu lasting 62 days in 2020 was the strongest summer precipitation in the Yangtze-Huaihe River basin (YHRB) of China since meteorological observations were recorded in 1961, causing more than 140 dead or missing people and USD 11.75 billion of economic losses. The monsoon characteristics of summer precipitation, such as the start and end date of the Meiyu, the intensity of precipitation, and the appearance of the inverted Meiyu, can cause extreme meteorological disasters such as floods and droughts, which have huge socio-economic impact on the local area because of large population and intensive agricultural production in MYA. It usually starts in mid-June and ends in mid-July, marking the beginning of the summer monsoon in the northern hemisphere subtropical regions and the beginning of the rainy season in East Asian temperate regions, respectively, showing its importance as a member of the EASM system. The most prominent feature of local precipitation is the Meiyu, which is also called Changma in Korea and Baiu in Japan, a quasi-stationary rain belt from the lower reaches of the Yangtze River (LRYR) to southern Japan. The Meiyu area (MYA) is a concentrated area of East Asian subtropical summer rainfall, reflecting the characteristics of the East Asian summer monsoon (EASM). The structure of CEOF2 is somewhat induced by local SSTAs over the Northern Indian Ocean and South China Sea. At the same time, there is a radical reversion from abnormal eastly to westly wind in the upper troposphere. The corresponding geopotential height circulation of positive CEOF2 shows the large negative anomaly in the region north of 40° N and a positive anomaly over Japan in June, whereas the pattern reverses in July. The second mode shows an opposite precipitation anomaly in June and July, and the distribution in August is not significant. The positive CEOF1 is preceded by decay of El Niño episodes, including the abnormal warm sea surface temperature anomalies (SSTAs) in the equatorial Central-Eastern Pacific in spring and warm SSTAs in the equatorial Indian Ocean in summer. The positive (negative) CEOF1 is accompanied by the negative (positive) East Asia/Pacific pattern, including strong westerly wind anomalies in the upper troposphere and southwest monsoon in the lower troposphere, and the Western Pacific Subtropical High extending westward and its ridge line slightly south. The first mode of the intraseasonal variations shows an in-phase pattern over the Meiyu area in June, July, and August, accounting for 22.2% of the total variance in the intraseasonal variations of summer precipitation anomalies. The intraseasonal variations of summer precipitation anomalies in the Meiyu area of East Asia are analyzed by applying a combined empirical orthogonal function (CEOF) of the latest meteorological reanalysis data ERA5 of European Center for Medium-Range Weather Forecasts for the period from 1991 to 2020, and the circulation structures and sources of variability of CEOF are also investigated.
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