四川省近60年夏季夜雨时空变化特征

Temporal and Spatial Variations of Summer Night Rain in Sichuan Province in the Last 60 Years

为更有效地对四川省近60 a夏季夜雨的时空变化特征进行分析与研究,利用四川省126个气象台站1961-2019年的逐日降水数据资料,采用线性趋势估计法、Mann-Kendall突变检验、Morlet小波分析法和旋转经验正交函数分解(REOF)等方法,分析四川省夏季夜雨的时空变化特征。结果表明:四川省夏季夜雨量的空间分布为东多西少、南多北少型,四川省大部地区夜雨率占50%以上,最高的川南和雅安等地夜雨率可达70%以上,夏季夜雨量整体呈下降趋势,空间分布为西增东减,夜雨相对变率大值中心出现在川东北部,其相对变率数值在2倍以上,最高值中心的阆中、剑阁和旺苍3地可达到6倍。四川省夏季夜雨量REOF分析表明可以分为川西高原区(Ⅰ区)、川西南山地区(Ⅱ区)、川西北区(Ⅲ区)、川东南区(Ⅳ区)和川东北区(Ⅴ区)。四川省夏季夜雨量长期变化趋势显著,其中Ⅰ、Ⅱ、Ⅴ区夏季夜雨量呈现明显上升趋势,Ⅲ、Ⅳ区夏季夜雨量则出现下降趋势。上述各区域夜雨量突变的时间点主要发生在1970年代附近,四川省夏季夜雨量变化周期特征为长周期内包含有短周期并存在周期性的振荡,且在5个区域内夏季夜雨的变化周期以20~30 a及5~10 a的周期最普遍。

To effectively analyze and study the temporal and spatial variation characteristics of summer night rain in Sichuan Province over the past 60 years,the daily precipitation data of 126 meteorological stations in Sichuan Province from1961 to 2019 were used to analyze the temporal and spatial variation characteristics of summer night rain in Sichuan Province in detail by using linear trend estimation,Mann Kendall mutation test,Morlet wavelet analysis and rotating empirical Orthogonal functions decomposition(REOF)and other methods.The results show that the spatial distribution of summer night rain in Sichuan Province is more in the east and less in the west,and more in the south and less in the north.The night rain rate in most areas of Sichuan Province accounts for over 50%,with the highest night rain rates in southern Sichuan and Ya'an reaching over 70%.The overall trend of summer night rain is decreasing,with a spatial distribution of increasing in the west and decreasing in the east.The center of the relative variability of night rain is located in northeastern Sichuan,with a relative variability value of over 2 times,and the highest value is located in Langzhong,Jiange,and Wangcang can reach up to six times.The REOF analysis of summer night rainfall in Sichuan Province shows that it can be divided into the western Sichuan plateau region(ZoneⅠ),the southwestern Sichuan mountain region(ZoneⅡ),the northwestern Sichuan region(ZoneⅢ),the southeastern Sichuan region(ZoneⅣ),and the northeastern Sichuan region(ZoneⅤ).The Secular variation trend of summer night rainfall in Sichuan Province is significant.The summer night rainfall in areasⅠ,Ⅱ,andⅤshows an obvious upward trend,while the summer night rainfall in areasⅢandⅣshows an opposite downward trend.The time points of sudden changes in night rain in the above regions mainly occurred near the 1970s.The cycle characteristics of summer night rain in Sichuan Province are characterized by long periods containing short periods and periodic oscillations,and the cycle of summer night rain in the five regions is most common with periods of 20-30 years and 5-10 years.