New Delhi: As heatwaves become increasingly common worldwide, Japanese researchers have found a new type of weather event in the island country—moist heatwaves.
The moist heatwave is unlike the ones on large continental masses. So far, extremely warm days have been associated with hot weather and dry land. As the land gets drier, evaporation falls, leading to low humidity and high temperatures for prolonged periods.
However, a recent study published in Springer Nature found the rise of a new type of heatwave, which is often accompanied by heavy rainfall and cyclones. The team of researchers from Tokyo Metropolitan University highlighted that such weather patterns are dangerous since they can trigger multiple natural hazards at the same time.
“Heatwaves in Western countries are often driven by mid-latitude weather systems, whereas those in Japan could be influenced by other factors, such as tropical convection patterns, which contribute to the development of the subtropical high near Japan,” the study said.
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What makes moist heatwaves dangerous
The team, led by associate professor Hiroshi G Takahashi, studied the air circulation patterns around the Japanese archipelago when the heatwaves hit. They extracted the airflow data for over 108 heatwave days from 1992 to 2021. Along with dry winds, they also found that the low-pressure conditions that accompany cyclones also led to higher temperatures. As a tropical cyclone nears Japan, it can often funnel warm and moist air from the nearby tropics straight into the Japanese archipelago.
Such moist heatwaves made up nearly one-fourth of the heatwaves in the past decade. Researchers highlighted that they seemed to be getting more frequent in the past 30 years.
The effects of moist heatwaves are far less studied. However, research has shown that humidity can affect the body’s capacity to sweat, which is its primary cooling mechanism. An excess of moisture in the air can prevent sweat from evaporating. Hot and humid air can also exacerbate conditions such as asthma and other lung diseases.
In 2018, Japan recorded devastating heat. Nearly 22,000 people were admitted to hospitals as temperatures rose over 40 degrees Celsius in several parts of the country. More than 1,000 people died that summer in Japan.
While climate change is a key driver of such temperature hikes, a lot of the research into extreme weather events remains focused on American and Eurasian planes.
The researchers highlighted that their discovery of moist heatwaves could be the first step in understanding how extreme weather affects maritime environments.
“Continued investigations using climate model experiments are essential to better understand the mechanisms, predictability, and future evolution of these moist heat waves under a warming climate,” the study said.
(Edited by Prasanna Bachchhav)