An analysis on characteristics of heavy rainfall processes during the Meiyu season in Jianghuai region

In order to facilitate the identification of heavy rainfall during the rainy season in the Yangtze River valley, an objective method to classify strong rainfall processes during the rainy season in Yangtze-Huaihe region is proposed, and the characteristics of heavy rainfall processes during the rainy season in Yangtze-Huaihe are analyzed. The results show that the method can effectively classify heavy rainfall processes during the rainy season in Yangtze-Huaihe, and the results are in good agreement with the existing results from operational forecasts. The method proposed in the present study is convenient for operational application. There exist obvious inter-annual variations in heavy rainfall process during the Meiyu period in the Yangtze-Huaihe region, which are closely related to the intensity of the Meiyu front in Yangtze-Huaihe region. There are more heavy rainfall processes and rainy days and shorter intervals between rainfall events in strong Meiyu years. Persistent, repetitive, heavy and frequent rainfall events are usually presented in strong Meiyu years in Yangtze-Huaihe region. The situations are opposite in weak Meiyu years. In the past 56 years, accumulative amount of heavy rainfall during the Meiyu period demonstrates a linear increasing trend in the entire Yangtze-Huaihe region, and the area of most obvious increase is located in southern Jiangsu and northern Zhejiang. Spatial distribution of accumulative rainfall is consistent with that of accumulated heavy rainfall days during the Meiyu period. The largest regional centers are located in southwestern Anhui, northeastern Jiangxi and eastern Hubei. According to results of the objective method proposed in this paper, the accumulated rainfall caused by heavy rainfall processes and the total precipitation in the Meiyu period have similar spatial and temporal variations.