Effect Of Variation Of East Asian Subtropical Summer Monsoon Processes On Meiyu Anomaly Over The Yangtze-Huaihe River

According to the consistent Meiyu criterion provided by China Meteorological Administration,the daily meteorological data of Meiyu at 661 stations in China during 1960~2016 and ncep/ncar monthly mean reanalysis data,this paper analyzes the Spatio-temporal variation characteristics of Meiyu and the variation of the East Asian subtropical summer monsoon,extracts the key areas(112°E~120°E,32°N~34°N,including 17 stations)of the monsoon and analyzes the links and genesis of the key areas of the monsoon and the Meiyu.The results show:The average rainy season in 1960~2016 is from June 8th to July 15 th,and the average rainfall is 303 mm.The onset time of the rainy season is 9 days earlier than that of the average time of the East Asia,which is 7 days later than the end of the rainy season.The amount of plum rains has fluctuated in the past 57 years,but the overall trend is rising.The earlier the plum season begins,the later the plum season ends,the longer the rainy season,the more the plum rains.The average time for the subtropical summer monsoon to advance to the key area is May 19 th.In the late 1970 s and late 1990 s,the subtropical summer monsoon suddenly changed from late to early and from early to late,respectively.When the summer monsoon reaches the key area early,the out of the plum day is late,and the amount of plum rain is high.When the summer monsoon reaches the key area late,the out of the plum day is early,and the amount of plum rain is low.The subtropical summer monsoon and the Meiyu rainfall are consistently negatively correlated with the whole region,and the negative correlation center is in Hunan.The East Asian subtropical summer monsoon reaches the key area early(late),the Ural Mountains ~ Okhotsk Sea is positive(negative)anomalies,and the blocking high pressure is enhanced(weakened).The pressure anomaly near the Sea of Japan is negative(positive),the East Asian trough is strengthened(weaked),strengthens(weaks)the cold air that is transported southward after the trough and does not(have)beneficial to the northern jump of the mid-low latitude subtropical high.The West Pacific subtropical high-pressure center is strengthened(weakened),and its position is westward(eastward).the southwestern warm and humid airflow of the northwestern side is strengthened(weakened),and the Jianghuai area has the convergence of water vapor(diverging),which is(not)conducive to the plum rain.When the SST anomalies in the Indian Ocean-South China Sea warm pool and the equatorial eastern Pacific are high(low),the Meiyu rainfall is high(low).When the SST anomalies in the western Pacific Ocean are high(low)and the SST anomalies in the equatorial eastern Pacific Ocean are low(high),the time for the East Asian subtropical summer monsoon to advance to the key area of the Yangtze River is late(early)and the Meiyu is early(late).