A team of international researchers from Pusan National University, South Korea, have found heatwaves to have intensified in duration and frequency over the past 60 years (1958–2019). 

 

The team led by Professor Kyung-Ja Ha from Pusan National University, South Korea, analysed the prevalence of the two types of heatwaves in East Asia.

 

According to their study, dry heatwaves occur mainly in northwestern East Asia, while moist heatwaves are prevalent over southern East Asia.

 

Using historical climate data, the team determined for the first time how and where these heatwaves form and also predicted the occurrence of heatwaves in the future under different greenhouse gas emission scenarios.

 

The research team found that these heatwaves tend to be frequent under favorable large-scale atmospheric conditions, which vary for dry and moist heatwaves.

 

“In dry heatwave regions, anticyclonic, that is clockwise circulation, is amplified after the onset of heatwaves under the influence of the convergence of anomalous wave activity flux over northern East Asia. This results in surface warming via adiabatic processes. In contrast, the moist heatwaves are triggered by the locally generated anticyclonic circulation anomalies, and surface warming in these cases is amplified by cloud and water vapor feedback,” explains Prof Ha.

 

The researchers then went on to analyse how increases in greenhouse gas emissions would affect heatwaves. The simulations revealed more frequent dry heatwaves and longer-lasting moist heatwaves even when greenhouse gas emissions were kept to a minimum to limit the temperature rise to 1.5 deg C, suggesting the need for further reductions in greenhouse gas emissions to avoid severe heatwave conditions.

 

Studying heatwaves by their types is essential as these events form under different conditions and lead to different outcomes. “Increases in dry heatwaves are expected to damage agriculture, while moist heatwaves can be extremely detrimental to the human body,” cautions Prof Ha. 

 

Identifying vulnerable regions can assist governing bodies in developing strategies that will mitigate the impacts of severe heatwaves.

 

This involves planning for increased electricity use in places at risk of experiencing moist heatwaves and managing water supplies in regions susceptible to dry heatwaves. -OGN