四川盆地夏季夜雨气候变化特征

Climate Change Characteristics of Summer Nighttime Precipitation in the Sichuan Basin

摘要: 为研究四川盆地夏季夜雨的时空变化特征，本文基于1961~2023年盆地82个气象站逐日降水资料，采用REOF分解、Morlet小波分析和EEMD分解等统计方法，分析了夏季(6~8月)夜雨量、夜雨日数和夜雨强度的空间分布格局、时间演变趋势及多尺度周期特征。结果表明：1) 四川盆地夏季夜雨具有显著的“西南高、东北低”空间分布格局，高值区集中于雅安–乐山–眉山一带。2) REOF分解结果反映盆地西南部夜雨偏强、东北部相对偏弱的基本空间结构。进一步将四川盆地划分为盆地西部、盆地东北部和盆地南部三个典型区域。3) 夜雨量时间演变的线性趋势不显著，年际波动主导变化；夜雨日数略有减少，而夜雨强度呈增强趋势，尤其21世纪以来高强度夜雨事件增多。4) 小波分析和EEMD对区域分析表明：盆地西部以4~8年和16~32年尺度最显著，东北部兼具5~6年和13年、22年周期，南部则表现出有3~4年的短周期变化，其次是6年、22年周期。

Abstract: To investigate the spatiotemporal characteristics of summer nighttime precipitation in the Sichuan Basin, this study uses daily precipitation data from 82 meteorological stations in the basin from 1961 to 2023, and employs REOF, Morlet wavelet analysis, and EEMD to analyze the spatial distribution patterns, temporal evolution trends, and multi‑scale periodic features of summer (June~August) nighttime rainfall amount, nighttime rainfall days, and nighttime rainfall intensity. The results are as follows: 1) Summer nighttime precipitation in the Sichuan Basin exhibits a distinct spatial pattern of “high in the southwest and low in the northeast”, with the high-value areas concentrated around the Ya’an-Leshan-Meishan region. 2) REOF results reveal a basic spatial structure in which nighttime rainfall is relatively stronger in the southwestern basin and weaker in the northeastern basin. Based on this, the Sichuan Basin is further divided into three typical subregions: the western basin, the northeastern basin, and the southern basin. 3) The linear trend of nighttime rainfall amount over time is not statistically significant, with interannual fluctuations dominating the variation. Nighttime rainfall days have decreased slightly, whereas nighttime rainfall intensity shows an increasing trend, and high-intensity nighttime rainfall events have become more frequent since the beginning of the 21st century. 4) Regional wavelet and EEMD analyses indicate that the western basin is dominated by 4~8-year and 16~32-year scales; the northeastern basin exhibits 5~6-year, 13-year, and 22-year cycles; and the southern basin mainly shows a short 3~4-year cycle, followed by 6-year and 22-year cycles.