四川省冬季昼雨的多尺度时间变化特征

Multi-Scale Temporal Variation Characteristics of Winter Daytime Rain in Sichuan Province

摘要: 利用为了研究四川省昼雨冬季的区域分布特征，利用四川省126个气象站1961~2021年共61年的逐日降水观测资料，通过旋转经验正交函数分解(Rotated Empirical Orthogonal Function Decomposition，以下简称REOF分解)和Morlet小波分析等多种现代气候诊断统计分析方法，较为详细地分析了四川省61年来冬季昼雨的时空分布特征。研究表明：(1) 四川省冬季昼雨位于川南部，中心值达到40 mm；冬季的昼雨日数最大值在川东南部，中心值达到40 d；冬季昼雨强度位于川西南山地，中心值达到0.1 mm/h。(2) 冬季昼雨的REOF分解结果表明：可分为川西南山地、川东北、川西北、川中南和川西高原5个区域。(3) 时间变化上，冬季昼雨趋势线在20世纪90年代从低于均值变成高于均值呈上升趋势，表明昼雨线性增加；冬季昼雨日数趋势线在20世纪90年代从高于均值变成低于均值呈下降趋势，表明昼雨日数线性减少；冬季昼雨强度趋势线在20世纪90年代从低于均值变成高于均值呈上升趋势，表明昼雨强度线性增强。(4) 小波分解表明冬季时：川西北有6年、14年周期变化；川东北部存在4年、15年周期变化；川西南山地有6年、14年周期变化；川中南部存在8年、19年周期变化；川西高原5年、12年周期变化。

Abstract: To investigate the spatial pattern of winter daytime rain across Sichuan Province, this study utilized daily precipitation observation data from 126 meteorological stations in Sichuan from 1961 to 2021 (a total of 61 years). Using a suite of modern climatic diagnostic tools—including Rotated Empirical Orthogonal Function (REOF) decomposition and Morlet wavelet analysis—we present a detailed picture of the temporal and spatial variability of winter daytime rain in Sichuan over the past six decades. The research indicates: (1) Winter daytime rain in Sichuan is anchored in the south, where totals top out near 40 mm, while the southeast logs the greatest number of wet days—about 40—and the southwest mountains register the highest intensities, peaking at roughly 0.1 mm/h. (2) The REOF decomposition results of winter daytime rain show that it can be divided into five regions: the southwestern Sichuan mountains, northeastern Sichuan, northwestern Sichuan, south-central Sichuan, and the western Sichuan plateau.(3) In terms of temporal variation, the trend line for winter daytime rain amount shifted from below average to above average in the 1990s, showing an increasing trend, which indicates a linear increase in daytime rainfall. The trend line for the number of winter daytime rain days shifted from above average to below average in the 1990s, showing a decreasing trend, which indicates a linear decrease in the number of rainy days. The trend line for the intensity of winter daytime rain shifted from below average to above average in the 1990s, showing an increasing trend, which indicates a linear intensification of rain intensity. (4) Wavelet analysis reveals periodic changes in winter for each region: Northwestern Sichuan has periods of 6 and 14 years; Northeastern Sichuan has periods of 4 and 15 years; the Southwestern Sichuan mountains have periods of 6 and 14 years; South-central Sichuan has periods of 8 and 19 years; and the Western Sichuan Plateau has periods of 5 and 12 years.