Unraveling the seasonal variability of meteorological droughts: multiscale insights into the coupling with atmospheric circulation factors
摘要
Amidst the ongoing challenges of climate change, droughts are projected to become more frequent and intense, posing significant risks to water resources and food security. The occurrence and progression of seasonal droughts and their driving mechanisms are becoming increasingly complex. This study examines the seasonal characteristics of meteorological droughts in the North China Plain (NCP) using the Standardized Precipitation Evapotranspiration Index (SPEI). Wavelet coherence (WTC) and multivariate wavelet coherence (MWC) were used to explore the coupling effects of atmospheric circulation factors (ACFs) on seasonal droughts. The results reveal pronounced seasonal differences. Drought events predominantly occur in spring and summer, with spring droughts being particularly severe. Seasonal drought exhibits distinct spatial patterns, with elevated spring drought risk in the northeast affecting the central region, intensified summer drought in the northwest, heightened autumn drought risk in the east with pronounced severity in Henan, and winter droughts are most substantial in the southern region. Seasonal droughts are influenced by different ACFs in each season. In spring, the negative phase of the West Pacific Index (WP), in conjunction with the Pacific Decadal Oscillation (PDO) and Indian Ocean Dipole (IOD), is associated with more frequent or severe droughts. During summer, drought conditions are intensified under the positive phase of the PDO combined with WP and El Niño (Niño3.4). In autumn, drought occurrence is more likely under the combined effects of the negative phase of the Southern Oscillation Index (SOI) and the IOD. In winter, the Niño3.4–SOI–Sunspot Count (Sunspot) combination, especially under the negative phase of Niño3.4, corresponds to increased drought risk. These findings provide critical insights into the mechanisms driving seasonal droughts and provide a valuable foundation for enhancing agricultural productivity and water resource management strategies in the NCP.