近40年湖南冰雹时空分布和变化特征及机理分析

Temporal and Spatial Distributions and Mechanism of Hails in Hunan in Recent 40 Years

利用湖南省1967～2006年近四十年冰雹日数资料,分析了湖南冰雹时空分布特征,着重讨论了湖南冰雹日数年代、年、季、月、旬、日际变化、地域分布特征及湖南前后二十年冰雹的变化趋势。研究表明:湖南冰雹是典型的春雹区,春季冰雹日数占全年冰雹日数的74.9%;存在2年和4.8年的周期;日变化十分明显,多出现在午后到傍晚;地理分布呈西多东少,高山多于平原,洞庭湖北侧多于南侧的特点;近二十年冰雹呈减少趋势,多雹区更集中,主要出现在湘西北和湘东南。

The temporal and spatial distributions of hails are studied based on the data of the number of hailing days in Hunan Province from 1967 to 2006. In particular, the changes and geographic distribution characteristics of inter-annual variations, inter-decadal, quarter, month and dekad of hail-days and the trend of hails during 40 years are analyzed. The result shows that Hunan is a typical spring-hail district. The hailing days in spring account for 74.9% of those in a year; they exist in a cycle of 2 to 4.8 years. The variation of hails is obvious in a day, often in the afternoon or evening. The geographic distribution of hails in Hunan： hail events occur more frequently in the west than in the east, more in the mountains than in the plains, and more in the north of Dongting Lake than in the south. The decreasing trends of hailing days are continued in recent 20 years. Hail regions are more concentrated than before, and mainly in the northwest and southeast of Hunan.