江淮梅雨季节强降雨过程特征分析

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

为了便于识别梅雨季节江淮地区的强降雨过程,促进汛期强降雨过程的预报方法研究,使用中国国家级地面气象站逐日观测资料,提出了一种划分江淮梅雨季节强降雨过程的客观方法,并对江淮梅雨季节内强降雨过程的特征进行了分析。结果表明:该方法能有效划分出江淮梅雨季节的强降雨过程,划分结果与预报业务中的划分结果具有较高的一致性,便于在业务中应用。在江淮梅雨季节内,梅雨期的强降雨过程存在明显的年际变化且与梅雨强、弱密切相关,强梅雨年具有较多的强降雨过程以及过程累积强降雨日,强梅雨年的强降雨过程具有持续性、反复性和频发性的特征。弱梅雨年则相反。近56年来梅雨期强降雨过程累积雨量在整个江淮地区有线性增加的趋势,且江苏南部至浙江北部地区雨量增大的趋势最为显著。梅雨期强降雨过程累积雨量及雨日的空间分布是一致的,最大区域中心均位于安徽西南部、江西东北部及湖北东部等地。按照此客观划分方法确定的梅雨期的强降雨过程累积雨量与梅雨期总雨量具有较为相似的时空变化特征。

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 YangtzeHuaihe 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.