Zonal and Dipole Patterns of Winter Precipitation in Southern China and Their Associated Circulation

This study investigates the distinct patterns of winter precipitation variability across southern China, a region encompassing the climatically vital Southwest China and South China subregions. Accurately diagnosing their coordinated variability is fundamental for advancing climate dynamics understanding, yet traditional approaches are often limited by inherent spatial heterogeneity in precipitation characteristics. To address this, we introduce a local standardization procedure prior to empirical orthogonal function analysis, effectively isolating the regionally coherent signal. This refined methodology reveals 2 statistically robust and physically distinct modes. The leading mode (41.4% of variance) is a zonal in-phase pattern, characterized by simultaneous precipitation anomalies across Southwest China and South China. It is synergistically modulated by the Eurasian wave train (EU2), which weakens the East Asian winter monsoon, the India–Burma Trough (IBT), enhancing moisture advection, and the tropical Indian–Pacific tripole sea surface temperature pattern, which intensifies ascending motion. The second mode (14.3% of variance) exhibits an east–west dipole pattern, predominantly governed by the Scandinavian teleconnection (SCAND). The negative phase of SCAND induces blocking high-pressure anomalies near Lake Baikal, prompting cold-air outbreaks that suppress precipitation over South China while concurrently blocking the eastward extension of the IBT, thereby concentrating moisture and increasing precipitation over Southwest China. Our findings elucidate the complex interplay of extratropical teleconnections and tropical forcing in shaping regional climate, and the methodological framework offers an improved approach for analyzing coordinated variability within heterogeneous domains.