Heatwaves in Southeast Asia and Their Changes in a Warmer World

• Published in: Earth's future Vol. 9; no. 7
• Main Authors: Dong, Zizhen, Wang, Lin, Sun, Ying, Hu, Ting, Limsakul, Atsamon, Singhruck, Patama, Pimonsree, Sittichai
• Format: Journal Article
• Language: English
• Published: Bognor Regis John Wiley & Sons, Inc 01.07.2021; Wiley
• Subjects: Amplitudes; Climate; Climate change; Daily temperatures; Datasets; Enthalpy; Extreme high temperatures; Global warming; Heat waves; heatwave; Labor productivity; Maximum temperatures; Older people; Precipitation; Regions; risk; Temperature extremes; Thailand; Southeast Asia
• ISSN: 2328-4277; 2328-4277
• DOI: 10.1029/2021EF001992

Based on the observational dataset SA‐OBS and model outputs from the Community Earth System Model Large Ensemble project, this study investigates heatwaves in Southeast Asia in the current and future warmer climate. A heatwave is detected when the daily maximum temperature exceeds the 90th percentile threshold at each grid for at least three consecutive days. Three characteristics describing the frequency, duration, and amplitude of heatwaves are examined, including the sum of heatwave days per year (HWF) satisfying the heatwave definition, the length of the longest yearly heatwave event (HWD), and the hottest amplitude of the hottest yearly heatwave event (HWA). Results indicate that increased global warming is associated with substantial changes in heatwave characteristics over Southeast Asia, with more frequent heatwaves, longer heatwave duration, and higher extreme temperatures. The increase in HWA has a linear growth against global warming levels with distinct regional differences between the Maritime Continent and the Indochina Peninsula due to their different heat content of lower atmospheric boundaries. In contrast, those in HWF and HWD have nonlinear growth characteristics. The projected warmer future tends to be associated with a higher risk ratio value with the occurrence of rarer extreme heatwaves relative to the current climate. These results reiterate the potential risks of extreme regional heatwaves if global warming is unrestricted. Plain Language Summary A heatwave denotes a prolonged period that the temperature is above a prescribed threshold for several consecutive days. It usually has adverse effects on human health and the ecosystem. However, there is little knowledge of heatwaves in tropical developing countries such as those in Southeast Asia. This study investigates three characteristics, including the frequency, duration, and amplitude, of the heatwaves in the current climate and their changes in the future warmer climate in Southeast Asia based on observational datasets and outputs from a state‐of‐the‐art model, the Community Earth System Model. Results indicate that global warming will lead to substantial changes in heatwaves over Southeast Asia. The changes are not uniform in space, especially between the Maritime Continent and the Indochina Peninsula, because the two regions have different types of land‐sea distribution. Nevertheless, a consensus is that more frequent heatwaves, longer heatwave duration, and higher extreme temperature during heatwaves will occur over entire Southeast Asia in a warmer world. These changes mean that a rare heatwave, such as that occurring once‐in‐50‐years in the current climate, will become common and happen more frequently in a warmer future. Key Points Global warming is associated with substantial increases in heatwave frequency, duration, and amplitude over Southeast Asia The increase of heatwave amplitude with global mean temperature is quasilinear, and that of heatwave frequency and duration are nonlinear A warmer future will see a higher risk ratio with rarer extreme heatwave events relative to the current climate