贵州省61年冰雹气候特征及其成因分析

CLIMATIC CHARACTERISTICS AND CAUSES OF HAIL IN GUIZHOU: 1961—2021

关键词:  冰雹  时空分布特征  EOF分解  小波分析  成因分析

Key words:  hail  temporal and spatial distribution characteristics  EOF decomposition  wavelet analysis  cause analysis

摘要:

选取1961—2021年贵州省84个国家站冰雹观测资料，运用回归分析、小波分析和EOF分解对贵州省近61年冰雹发生的时空分布特征进行研究，并通过分析大气环流和外强迫因子的异常，探究冰雹日数极端年份的成因。结果表明：贵州省一年四季均有冰雹，春季最多，秋季最少。冰雹出现时间以14—01时的午后到夜间为主。贵州省冰雹的发生有14年和8年的周期，1995年后主周期变短，出现频次减少。冰雹主要分布在中西部，年均冰雹频次与海拔呈正相关，EOF分解后，贵州省冰雹空间分布前两个模态在空间向量场上呈现为全省一致型和东西相反型，受大尺度环流及地形影响产生的冰雹为减少的趋势，1991年后贵州省中部以东受地形激发及局地对流产生的冰雹有略微上升的趋势，但其方差贡献率较小，因此贵州省整体冰雹日数为下降趋势。通过极端冰雹年的大气环流和外强迫因子的分析，发现La Ni?a年海温的异常激发了热带西北太平洋异常气旋，导致该地区副高偏弱，进一步影响到贵州及其周边的位势高度有负异常，不利于贵州省冰雹的发生，对应贵州的少雹年，而El Ni?o年则相反，对应贵州省的多雹年。

Abstract:

Based on the hail observational data from 84 national stations in Guizhou Province during 1961—2021, the temporal and spatial distribution of hail in Guizhou in recent 61 years were studied by using regression analysis, wavelet analysis and EOF decomposition. Anomalies of atmospheric circulation and external forcing factors were also adopted to analyze hail frequency. The results showed that hail can occur all year long in Guizhou with most in spring and least in autumn. On a daily scale, hail mainly occurred in the afternoon and evening from 14:00 to 01:00. The occurrence of hail in Guizhou showed oscillation cycles of 14 years and eight years, and the trend changed around 1995 with shorter oscillation and lower frequency. The central and western regions were more hail-prone, and the annual average hail frequency was positively correlated with altitude. After EOF decomposition, the first two modes of spatial distribution of hail in Guizhou were provincial consistent and east-west opposite in the spatial vector field. Hail caused by large-scale circulation and topography tended to decrease. After 1991, hail induced by terrain and local convection in the east of central Guizhou slightly increased, but its variance contribution rate was small. Therefore, the overall number of hail days in Guizhou exhibited a downward trend. Through the analysis of atmospheric circulation and external forcing factors, it was found that the anomaly of sea surface temperature in a La Ni?a year triggered abnormal cyclones in the tropical northwest Pacific, leading to a weaker Subtropical High in the region and further affected negative height anomalies in Guizhou and its surrounding areas, which was favorable for the occurrence of hail in Guizhou. By contrast, the number of hail events in Guizhou decreased in El Ni?o years.