Variations of Meiyu Indicators in the Yangtze-Huaihe River Basin during 1954-2003

1. IntroductionThe primary physical manifestation of the EastAsian summer monsoon is persistent, heavy precipita-tion identified with a coherent, well-defined rainband.Generally, such rainband movement is characterizedby a stepwise northward advance from southern Chinaand the western North Pacific in early-mid May to theYangtze River valley and southern Japan in mid-June,then to north China and the Yellow Sea as well as thesouthern Japan Sea in late July (Ding, 1992, 1994;Tao and Chen, …

Variations of Meiyu Indicators in the Yangtze-Huaihe River Basin during 1954-2003

To better understand climate variations of Meiyu, some new indicators for the onset and retreat dates,duration, and Meiyu precipitation in the Yangtze-Huaihe River valley are objectively developed by usingobserved daily precipitation data from 230 stations in eastern China during 1954-2003.The rainy season onset and retreat dates in each station can be defined in terms of thresholds for rainfallintensity and persistence. Then, the onset and retreat dates of the Meiyu for the Yangtze-Huaihe Riverbasin have been determined when more than 40% of stations reach the first rainy season thresholds in thestudy region.Based on the indicators of Meiyu in the Yangtze-Huaihe River basin, variations of Meiyu rainfall during1954-2003 are analyzed. The results suggest that Meiyu rainfall in the Yangtze-Huaihe River basin hasincreased in recent 50 years. In addition, interannual and interdecadal variability of Meiyu is also obvious.All the indicators display a predominant period of about 3 years.