Decadal variability of the integrated warm-wet conditions over China and its modulation by the pacific decadal oscillation

Abstract

The integrated warm-wet conditions across China, represented by the Warm-Wet Index (WWI), exhibit pronounced interdecadal variability during 1960–2022. Understanding the large-scale climatic drivers of this variability is essential for elucidating the mechanisms underlying long-term climate changes over China. In this study, Ensemble Empirical Mode Decomposition (EEMD) was applied to extract the interdecadal component of the WWI and investigate its relationship with the Pacific Decadal Oscillation (PDO). The association between the nationally averaged WWI and the PDO index was examined, together with the corresponding sea surface temperature anomalies and atmospheric circulation patterns, to explore the physical mechanisms linking PDO variability to regional warm-wet conditions. The nationally averaged WWI exhibits a significant correlation with the PDO index, indicating a robust interdecadal association between oceanic variability and regional climate over China. During positive PDO phases, sea surface temperature anomalies in the tropical central-eastern Pacific and the Indian Ocean are associated with an East Asia–Pacific (EAP)-like teleconnection pattern, accompanied by anomalous cyclonic circulation over most of China. This circulation favors enhanced upward motion and moisture convergence over southeastern China, Northeast China, and northern Xinjiang, thereby increasing precipitation and strengthening warm-wet conditions. Conversely, anomalous subsidence prevails over North China and the Tibetan Plateau, suppressing precipitation and weakening the WWI. These contrasting regional responses produce a distinct meridional tripole pattern in the WWI, with enhanced warm-wet conditions in Northeast China, northern Xinjiang, and southeastern coastal regions, and weakened warm-wet conditions over North China and the Tibetan Plateau. Opposite spatial patterns occur during negative PDO phases. The results suggest that the PDO modulates interdecadal warm-wet variability over China primarily through atmospheric circulation changes that influence precipitation. This ocean–atmosphere–land linkage provides further insight into the mechanisms governing long-term climate variability over China and offers a scientific basis for climate risk assessment and adaptation in the context of ongoing global warming.