Changed Relationships Between the East Asian Summer Monsoon Circulations and the Summer Rainfall in Eastern China

• Published in: Acta meteorologica Sinica Vol. 28; no. 6; pp. 1075 - 1084
• Main Author: 高辉 蒋薇 李维京
• Format: Journal Article
• Language: English
• Published: Heidelberg The Chinese Meteorological Society 01.12.2014; National Climate Center, China Meteorological Administration, Beijing 100081%Jiangsu Climate Center, Jiangsu Meteorological Bureau, Nanjing 210000
• Subjects: Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Earth and Environmental Science; Earth Sciences; Freshwater; Geophysics and Environmental Physics; Marine; Meteorology; 东亚夏季风; 中国东部地区; 全球气候变暖; 夏季降水; 夏季风环流; 西太平洋副热带高压; 西太平洋副高; 非对称特性; China, People's Rep., Changjiang R; precipitation; blocking high; western Pacific subtropical high; East Asian summer monsoon
• ISSN: 0894-0525; 2095-6037; 2198-0934; 2191-4788
• DOI: 10.1007/s13351-014-4327-5

In previous statistical forecast models,prediction of summer precipitation along the Yangtze River valley and in North China relies heavily on its close relationships with the western Pacific subtropical high（WPSH）,the blocking high in higher latitudes,and the East Asian summer monsoon（EASM）.These relationships were stable before the 1990 s but have changed remarkably in the recent two decades.Before the 1990 s,precipitation along the Yangtze River had a significant positive correlation with the intensity of the WPSH,but the correlation weakened rapidly after 1990,and the correlation between summer rainfall in North China and the WPSH also changed from weak negative to significantly positive.The changed relationships present a big challenge to the application of traditional statistical seasonal prediction models.Our study indicates that the change could be attributed to expansion of the WPSH after around 1990.Owing to global warming,increased sea surface temperatures in the western Pacific rendered the WPSH stronger and further westward.Under this condition,more moisture was transported from southern to northern China,leading to divergence and reduced（increased） rainfall over the Yangtze River（North China）.On the other hand,when the WPSH was weaker,it stayed close to its climatological position（rather than more eastward）,and the circulations showed an asymmetrical feature between the stronger and weaker WPSH cases owing to the decadal enhancement of the WPSH.Composite analysis reveals that the maximum difference in the moisture transport before and after 1990 appeared over the western Pacific.This asymmetric influence is possibly the reason why the previous relationships between monsoon circulations and summer rainfall have now changed.