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 using observed 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 rainfall intensity and persistence. Then, the onset and retreat dates of the Meiyu for the Yangtze-Huaihe River basin have been determined when more than 40% of stations reach the rst rainy season thresholds in the study region. Based on the indicators of Meiyu in the Yangtze-Huaihe River basin, variations of Meiyu rainfall during 1954-2003 are analyzed. The results suggest that Meiyu rainfall in the Yangtze-Huaihe River basin has increased 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.