Revealing the Circulation Patterns Most Conducive to Regional Heatwave in Southeast Asia and the Mechanisms Behind

Abstract

The increasing frequency of heatwaves over Southeast Asia (SEA) is impacting human health, infrastructure and economies. Understanding the relationship between large-scale circulation patterns and heatwaves is crucial for improving predictions and reducing damages. In this study, four distinct circulation patterns conducive to SEA heatwaves are identified by the self-organizing map. Three circulation patterns are associated with high-pressure systems over the mid-latitude Western Pacific and SEA, significantly influenced by El Niño–Southern Oscillation (ENSO). In addition to these common high-pressure patterns, a low-pressure dominant pattern is identified, characterized by two enhanced low-pressure systems over the Tibetan Plateau and mid-latitude Western Pacific, which deplete a considerable amount of moisture, resulting in diminished cloud cover and rapid warming across continental SEA. Further analysis reveals that all patterns are significantly modulated by Madden Jullian Oscillation (MJO) activities, each showing distinct peak occurrences in different MJO phases, with further links to ENSO and the Indian Ocean Dipole.