四川省春季昼雨气候变化特征

Climate Change Characteristics of Spring Daytime Rain in Sichuan Province

摘要: 为了研究四川省春季昼雨的区域分布特征，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)、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年来春季昼雨的时空分布特征。研究表明：(1) 四川省春季昼雨空间分布不均匀，春季昼雨空间分布均表现为东多西少、南多北少的型态，其中春季时的大值中心位于东北部，中心达到340 mm。春季的昼雨日数最大值在康定、雅安、峨眉一带，中心值达到40天。春季的昼雨强度大值分布位于川东部，大致中心达到0.2 mm/h。(2) 春季昼雨的REOF分解结果表明：春季昼雨可分为川南、川东北、川西北、川西高原和川西南山地5个区域。(3) 时间变化上，春季昼雨趋势线在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；春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，而昼雨强度与之相反，春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) 小波分析得出，春季时川西北有准8年、准18年周期变化；川西南山地有准8年、准25年周期变化；川西高原有准7年、准21年周期变化；川南有准7年、准15年周期变化；川东北部有准6年、准16年周期变化。

Abstract: To study the regional distribution characteristics of spring daytime rainfall in Sichuan Province, data from 126 meteorological stations across Sichuan Province over a period of 61 years (1961~2021) were utilized. Using modern climate diagnostic statistical methods, including rotated empirical orthogonal function decomposition (REOF decomposition) and Morlet wavelet analysis, a detailed analysis was conducted on the spatiotemporal distribution characteristics of spring daytime rainfall in Sichuan Province over the past 61 years. The study reveals: (1) The spatial distribution of spring daytime rainfall in Sichuan Province is uneven, generally showing more rainfall in the east and west, and more in the south and north. The peak value during spring is located in the northeastern part of the province, reaching 340 mm. The area with the highest number of spring daytime rainfall days is around Kangding, Ya’an, and Emei, with a central value of 40 days. The maximum intensity of spring daytime rainfall is found in eastern Sichuan, with a central value of approximately 0.2 mm/h. (2) The REOF decomposition results indicate that spring daytime rainfall can be divided into five regions: southern Sichuan, northeastern Sichuan, northwestern Sichuan, western Sichuan Plateau, and southwestern Sichuan mountainous areas. (3) In terms of time changes, the trend line for spring daytime rainfall shifted from below to above the mean in the 1990s, indicating a linear increase in daytime rainfall. The trend line for the number of spring daytime rainfall days shifted from above to below the mean in the 1990s, indicating a linear decrease in the number of rainy days. However, the intensity of daytime rainfall showed an opposite trend, with the trend line for spring daytime rainfall intensity shifting from below to above the mean in the 1990s, indicating a linear increase in daytime rainfall intensity. (4) According to wavelet analysis, in spring, the northwest of Sichuan exhibits quasi-8-year and quasi-18-year cycles; the mountainous areas of southwestern Sichuan show quasi-8-year and quasi-25-year cycles; the western plateau of Sichuan has quasi-7-year and quasi-21-year cycles; southern Sichuan has quasi-7-year and quasi-15-year cycles; and northeastern Sichuan has quasi-6-year and quasi-16-year cycles.