Characteristics and Trends of different types of Heatwaves over Southeast Asia based on ERA5-Land

Southeast Asia is characterized by high temperatures and humidity, and as urbanization accelerates and climate change intensifies, the region faces an increasing risk of heatwaves. This study investigates the characteristics and trends of heatwaves across Southeast Asia from 1960 to 2024. Using the ERA5-Land dataset, we classify heatwaves into three types—daytime, nighttime, and compound—based on four extreme temperature indices and consecutive days. The trends of these heatwave types are analyzed using the Mann-Kendall (MK) test and Sen's slope estimator. Additionally, we assess heat exposure intensity using the Heatwave Cumulative Intensity Index (HWCI) across five major Southeast Asian regions (Borneo, Java, the Malay Peninsula, Sumatra, and the Mekong Delta), with a focus on the potential health risks associated with prolonged temperatures exceeding threshold values.

The results reveal that nighttime and compound heatwaves are experiencing a significant upward trend, whereas daytime heatwaves do not show such a trend. Coastal areas exhibit longer durations and a marked increase in nighttime heatwaves, with approximately one additional heatwave event every decade, each lasting 1-2 days longer. In the analysis of HWCI, we find that the intensity of different heatwave types remains consistent across regions. Urbanization and land use/land cover changes do not significantly influence the overall heatwave trends, suggesting that heatwaves in Southeast Asia are predominantly driven by global warming and large-scale atmospheric-oceanic phenomena. This study underscores the urgent need to enhance heatwave monitoring systems and adaptation strategies for tropical low-latitude cities.