Differences between Two Types of India–Burma Trough Events in Wintertime: Local versus Eastward-Moving

Abstract Topographic forcing along the southeastern Qinghai–Tibetan Plateau favors bifurcation of the India–Burma Trough (IBT)—a critical weather system modulating Asia winter precipitation—into two archetypes with distinct dynamic mechanisms and climatic impacts. Short-lived local IBTs (17 events per year; mean 2.2 days) remain confined west of 100°E with shallow vertical structure (300 hPa). Triggered by intense mid–high-latitude disturbances (40°–60°N) over western Europe, their sustained cross-regional movement involves coordinated wave trains: energy injection along the subtropical westerly jet sustains the IBT development, while wave train along the polar jet weakens the East Asian trough to reduce cold-air resistance, thus favor IBT moving to eastward downstream. This process occurs within strong westerly anomalies and deep moist layers, interacting with the secondary circulation of the upper-level jet to facilitate IBT maintenance and eastward movement. We establish that large-scale circulation coordination—not local forcing alone—governs this dichotomy, creating fundamentally distinct regimes: 1) High-frequency/short-lived/localized events with limited impacts versusv 2) low-frequency/long-lived/high-impact systems exhibiting efficient energy conversion and extensive moisture transport that drive regional precipitation extremes.