Much of South Asia suffered from severe temperatures in 2022 due to unrelenting heat waves from March to April. German researchers from Johannes Gutenberg University Mainz and IIT-Bombay have discovered a complex mechanism underlying these occurrences, demonstrating a dynamic interaction between dry soil, air winds, and rising temperatures. Their results demonstrate how wind patterns and dry soil fueled 2022 heatwaves, creating new difficulties for the area.

The Impact of Atmospheric Winds on the Heatwave of March

An abrupt increase in the amplitude of short-lived atmospheric Rossby waves—large-scale undulations in high-altitude winds akin to river bends—was the primary cause of the March heatwave. According to lead author Roshan Jha, these waves grew stronger as energy was transferred from the extratropical jet stream near the poles to the subtropical jet stream near the equator. Temperatures reached previously unheard-of heights due to this energy transfer, which was exacerbated by the closeness of these wind systems during the heatwave. The work emphasises how vital these high-altitude dynamics were in causing the initial heat surge and was published in the Journal of Geophysical Research: Atmospheres.

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Dry Soil Amplifies April’s Heatwave Intensity

On the other hand, the April heatwave was caused by ground-level circumstances as opposed to atmospheric factors. The ground lost its capacity to control heat after March’s sweltering heat and clear skies dried up the soil. “When soil retains moisture, solar energy is used for evaporation rather than heating the air,” said Prof. Arpita Mondal, an IIT-B coauthor. However, all of that energy raises the air temperature in dry soil. This effect was exacerbated by heat from Pakistan and Afghanistan, which spread unrestrained throughout the region. The study cautions that this drying effect creates a feedback loop that prepares the area for even more severe heat waves. It was published in the Journal of Geophysical Research: Atmospheres.

“Understanding these mechanisms is vital for forecasting and preparing for extreme heat in South Asia,” said Prof. Subimal Ghosh, underscoring the significance of these results. Identifying these causes improves forecast and mitigation efforts as wind patterns change due to climate change. The study emphasises a cascade effect, in which wind patterns and dry soil fueled 2022 heatwaves, causing soil moisture to decrease, paving the way for another. As the region has a more unstable climate, this cycle of extremes highlights the urgent need for adaptive policies to safeguard vulnerable populations.

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