Journal Article

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

Wang, Jingyu, Zhu, Shoupeng, Lee, Joshua, Park, Edward, Zhang, Hugh, Ji, Yan, Lyu, Yang, Wang, Xianfeng, Fan, Yi, Zhi, Xiefei

2025

Overview

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. Plain Language Summary Heatwaves in Southeast Asia are becoming more frequent, damaging infrastructure and hurting the economy. Understanding how large weather patterns contribute to heatwaves can improve prediction and reduce their impacts. This study identifies four specific weather patterns that lead to heatwaves in Southeast Asia using the self‐organizing map method. Of these, three patterns are associated with the high‐pressure systems over the mid‐latitude Western Pacific and Southeast Asia, which contribute to 85.4% of total regional heatwave events and are affected by the El Niño–Southern Oscillation. These patterns can be summarized as the “uniform high” pattern, the “southern high and northern low” pattern and the “southern low and northern high” pattern, respectively. Besides the common high‐pressure dominant patterns, we also find a low‐pressure dominant pattern that causes heatwaves. This pattern involves two strong low‐pressure systems over the Tibetan Plateau and the mid‐latitude Western Pacific, which reduce moisture and cloud cover, leading to rapid warming in continental Southeast Asia. This low‐pressure pattern mostly happens during active phases 3–4 of the Madden‐Julian Oscillation and is modulated by the Indian Ocean Dipole. This work offers important insights into the physical mechanisms behind heatwaves and holds potential values for improving the forecasting of heatwaves in Southeast Asia. Key Points Four distinct circulation patterns conducive to Southeast Asia heatwaves are identified by self‐organizing map Three circulation patterns are linked to high‐pressure dominance, influenced by ENSO and could trigger extensive heatwaves over entire SEA A low‐pressure dominant pattern is also identified, modulated by Indian Ocean Dipole and Madden Jullian Oscillation, and tends to trigger intense heatwaves over continental SEA

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Circulation / Circulation patterns / Cloud cover / Damage detection / Damage patterns / Dipoles / El Nino / El Nino phenomena / El Nino-Southern Oscillation event / Heat waves / Infrastructure / Latitude / Madden-Julian oscillation / Moisture content / Oceans / Pressure / Pressure patterns / Southern Oscillation / Water content / Weather / Weather patterns