[Science Column] "Sticky Heatwaves in Southeast Asia, Parched Heatwaves in Central Asia"... The Two Faces of Asian Heatwaves

GIST Distinguishes Between "Humid Heatwaves" and "Dry Heatwaves" Through 50-Year Analysis
Region-Specific Responses Needed

A new study has found that heatwaves across the Asian continent do not manifest in the same way everywhere.

According to an analysis of 50 years of data by a research team at Gwangju Institute of Science and Technology (GIST), 'humid heatwaves' have been intensifying in monsoon regions such as Southeast Asia and the Korean Peninsula, while 'dry heatwaves' have become more pronounced in inland arid regions such as Central Asia and West Asia.

This study, led by Professor Yoon Jinho of the Department of Environmental Energy Engineering at GIST as part of an international collaboration, is the first to quantitatively analyze the combined effects of temperature and humidity on a continental scale to classify heatwave types across Asia. The findings were published in the latest issue of the international journal Climatic Change.

Comparison of temperature-based heatwaves and wet-bulb temperature-based heatwaves. (a) Spatial distribution of the difference between temperature-based heatwaves and wet-bulb temperature-based heatwaves during periods P1 (2000-2011) and P2 (2012-2023) in the monsoon region. (c) Time series changes of the difference between the two types of heatwaves in the monsoon region. (b) and (d) show the results for the arid region, corresponding to (a) and (c), respectively. Larger values (brown > 0) indicate that temperature-based heatwaves occurred more frequently, while smaller values (red < 0) indicate that wet-bulb temperature-based heatwaves occurred more frequently. In the monsoon region, as humidity increased, humid heatwaves (red) became more frequent, whereas in the arid region, where humidity changes were minimal, dry heatwaves (brown) intensified. Provided by the research team

The Two Types of Asian Heatwaves Revealed by 50 Years of Climate Data

The research team conducted a detailed analysis of summer (June to August) temperature and humidity data in Asia over the past 50 years (1973-2023) using the high-resolution climate reanalysis data (ERA5) from the European Centre for Medium-Range Weather Forecasts (ECMWF). The results showed that in monsoon regions, a combination of factors-including moisture influx from the ocean, urbanization, and the expansion of irrigation-

has led to a rapid increase in 'humid heatwaves' (compound heatwaves) characterized by simultaneous rises in temperature and humidity.

In particular, in areas such as the Indo-Gangetic Plain and southern China, the increase in relative humidity, rather than temperature, was identified as the main driver of intensified heatwaves. This impedes sweat evaporation, making it difficult for the human body to regulate temperature and sharply increasing heat stress. According to the study, the number of 'humid heatwave days' in monsoon regions has increased by an average of 1.95 days per year over the past decade.

In contrast, in arid regions such as Central Asia and West Asia, 'dry heatwaves' characterized by sharp rises in temperature alone have become more severe. In these environments with minimal moisture influx, the number of dry heatwave days has increased by an average of 2.05 days per year over the past decade, which the researchers warn could have a significant negative impact on agricultural productivity and water resource management.

Professor Jinho Yoon of the Department of Environmental Energy Engineering at Gwangju Institute of Science and Technology (GIST) (left) and Dr. Jina Park. Provided by GIST

"Climate Response Requires Region-Specific Strategies"

Professor Yoon Jinho emphasized, "Even with the same temperature rise, the pattern of heatwaves differs completely due to regional differences in moisture balance. Monsoon regions must prepare for 'humid heatwaves' that exceed the physiological limits of the human body, while arid regions need to address 'extreme heatwaves' that threaten agriculture and water resources."

Dr. Park Jina, co-first author from GIST, stated, "In regions with higher humidity, heat stress indices rise explosively, increasing health risks. Climate policies must consider not only temperature increases, but also the combined effects of humidity."

This research was conducted with the participation of Professor Kim Hyungjun of Korea Advanced Institute of Science and Technology (KAIST), Professor Jung Jihoon of Sejong University, and Dr. Moon Suyeon of the APEC Climate Center, and was supported by the Mid-Career Researcher Program of the Ministry of Science and ICT and the National Research Foundation of Korea.