1968—2017年湖南省冰雹时空分布特征

基于湖南省92个站点1968—2017年冰雹观测资料,采用回归分析、小波分析、主成分分析等方法,研究了湖南冰雹时空分布特征。结果表明,湖南近50年冰雹天气年际下降趋势显著,近20年来有记录的冰雹天气发生频次明显降低。湖南初次降雹的时间都集中在1—3月。冰雹月季变化显著,一年中以3月冰雹最多,2月的次之,从5月份起雹日骤然减少。春季是降雹最多的季节,占雹灾总数的56.06%,冬季的次之,夏季和秋季冰雹发生频率分别仅为全年的2.53%和0.69%。年冰雹日数主要存在4~5 a和19 a左右的振荡周期,20世纪90年代前还存在明显的9~10 a的振荡周期。各季节冰雹日数振荡周期不一。湖南冰雹空间分布呈自湘西北向湘东南递减的规律,年冰雹日数的空间分布特征与春季、冬季冰雹分布特征相似。湘北和湘中地区冰雹天气年际变化以下降趋势为主,湘南地区其气候趋势变化不明显。对湖南近50年冰雹日数进行主成分分析的前3个主要模态,在空间向量场上分别呈现出全省一致型、地势主导型和南北呼应型。

Spatial-Temporal Distribution Characteristics of Hails in Hunan Province from 1968 to 2017

Based on the hail observation data of 92 stations in Hunan Province from 1968 to 2017,the temporal and spatial distribution characteristics of hail events in Hunan Province are studied by using regression analysis,wavelet analysis,principal component analysis and other methods.The results show that the interannual variation of the hail weather in Hunan has decreased significantly in recent 50 years,and the frequency of recorded hail weather has decreased significantly in recent 20 years.The first occurrence time of hail events in Hunan is mainly concentrated in January-March.The monthly variation of hail is remarkable.During a year,hail occurs most in March,followed by February,and the hail days decrease sharply from May.Spring is the season with the most hail occurrences,accounting for 56.06%of the total hail disasters,followed by winter.The occurrence frequency of summer and autumn hails is only 2.53%and 0.69%of the annual hail frequency,respectively.The annual hail days mainly have oscillation periods of 4—5 years and about 19 years,but the oscillation period of 9—10 years appeared obviously before 1990s.The oscillation periods of hail days are different in each season.The spatial distribution of hail events in Hunan decreases from northwest to southeast.The spatial distribution characteristics of the annual hail days are similar to those in spring and winter.The interannual variation of hail weather in northern and central Hunan is dominated by a decreasing trend,while that in southern Hunan is not obvious.Based on the principal component analysis of hail days in Hunan in recent 50 years,the first three modes of principal component analysis of the hail days in Hunan Province in the past 50 years show,in the spatial vector field,the consistent type,the terrain dominant type and the north-south echo type,respectively.