Abstract:

Investigating the spatiotemporal characteristics of drought in western Guangdong and their correlation mechanisms with circulation indices is of great significance for regional disaster early warning and agricultural meteorological services. Meteorological data from 13 stations in western Guangdong during 1973-2022 and atmospheric circulation indices were used to calculate the multi-scale standardized precipitation evapotranspiration index (SPEI). Trend analysis, correlation analysis, and cross wavelet transform were applied to analyze the spatiotemporal drought characteristics and their correlations with circulation indices in western Guangdong over the past 50 years. The results showed that the annual, spring, and summer SPEI exhibited a drying trend in western Guangdong. The climate tendency rate reached -0.24 per decade in Huazhou and Yangchun, which were the centers of spring drying, with annual-scale drying dominated by precipitation decrease. Drought intensity in western Guangdong was mainly light to moderate. Although droughts occurred frequently in autumn and winter, their long-term trends were not significant. The correlation coefficient analysis indicated that spring drought was significantly correlated with the northward shift of the subtropical high ridge line over the South China Sea and the positive phase of the Western Pacific (WP) index in the preceding winter, while autumn drought was associated with the northward shift of the subtropical high ridge line six months earlier, a contracted Northern Hemisphere polar vortex nine months earlier, and the synergistic suppression of precipitation by positive phases of the Pacific Decadal Oscillation (PDO) index and Pacific-North American pattern (PNA) index. Cross-wavelet transform analysis indicated that the interdecadal variability of drought in western Guangdong was dominated by a 5-10 a periodicity associated with the PDO and subtropical high, which set the drought background, superimposed by inter-annual fluctuations driven by a 3-5 a periodicity of the Southern Oscillation Index (SOI) and the Northern Hemisphere polar vortex area index. During 1995-2005, the annual-scale SPEI indicated a negative phase resonance with the PDO, WP, and the South China Sea subtropical high ridge position index at a 5-10 a period, lagging behind the PDO by approximately 3 months. During 1996-2002, the annual-scale SPEI exhibited a negative phase resonance with the SOI and the Northern Hemisphere polar vortex area index at a 3-5 a period, lagging behind polar vortex area changes by approximately 9 months.

Key words: climate change, meteorological drought, standardized precipitation evapotranspiration index, atmospheric circulation index, cross wavelet transform

摘要：

探究粤西干旱时空特征及其与环流指数的关联机制，对区域灾害预警和农业气象服务具有重要意义。利用1973—2022年粤西13个气象观测站数据，计算多尺度标准化降水蒸散指数（Standardized Precipitation Evapotranspiration Index，SPEI），结合趋势分析、相关分析和交叉小波变换等方法，探讨粤西近50 a干旱时空特征及其与环流指数的相关关系。结果表明：粤西年、春季、夏季的SPEI均呈干旱化趋势，春季以化州和阳春为干旱化中心，气候倾向率均为-0.24·（10 a）^-1，年尺度干旱化由降水减少主导。粤西干旱等级以轻到中度为主，秋、冬季干旱频发，但其长期变化趋势并不显著。相关系数分析表明，春旱与南海副热带高压脊线位置偏北、前冬西太平洋遥相关型（West Pacific Pattern，WP）指数正位相显著相关；秋旱与前6个月的副热带高压脊线偏北、前9个月北半球极涡面积收缩、太平洋涛动（Pacific Decadal Oscillation Index，PDO）指数或太平洋-北美遥相关型（Pacific-North American Pattern，PNA）指数正位相协同抑制降水有关。交叉小波分析显示，粤西干旱的年代际变化由PDO、副热带高压主导的5~10 a周期决定干旱背景态，南方涛动指数（Southern Oscillation Index，SOI）、北半球极涡面积指数主导的3~5 a周期叠加年际波动。年尺度SPEI与PDO、WP、南海副热带高压脊线位置指数在1995—2005年存在5~10 a的负位相共振关系，显著滞后于PDO约3个月；年尺度SPEI与SOI、北半球极涡面积指数在1996—2002年呈现出周期为3~5 a的负位相共振关系，滞后于极涡面积变化约9个月。

关键词: 气候变化, 气象干旱, SPEI干旱指数, 大气环流指数, 交叉小波