Researchers at the Indian Institute of Technology Bombay (IITB), in collaboration with Johannes Gutenberg-University Mainz in Germany, have identified distinct climatic drivers behind the series of extreme heat events experienced in South Asian countries, including India, Pakistan, and Afghanistan. The study, published in the Journal of Geophysical Research: Atmospheres, focused on unusually intense heatwaves that occurred in March and April of 2022, uncovering how different atmospheric processes compounded the impacts of these events, resulting in temperatures far exceeding seasonal norms.
According to the findings, the March 2022 heatwave was linked to a sudden increase in the amplitude of short-lived atmospheric Rossby waves. These are large-scale oscillations in high-altitude winds that resemble bends in a winding river. Lead author Roshan Jha, a doctoral student at the Centre for Climate Studies at IIT Bombay, explained that the amplification of these waves was caused by energy transfer between westerly winds near the poles (extratropical jet stream) and westerly winds closer to the equator (subtropical jet stream). “The waves grew stronger as the two jet streams came closer during the heatwave,” Jha said.
The April 2022 heatwave, on the other hand, emerged through a completely different mechanism. Instead of being driven by wind patterns in high altitudes, it was primarily caused by very dry soil conditions combined with heat carried into India from the northwestern regions of Pakistan and Afghanistan. Notably, the dry soil conditions were exacerbated by the earlier March heatwave, which had already removed moisture from the ground through its high temperatures and clear skies.
The researchers highlighted a worrying feedback loop: one heatwave can set the stage for another, more severe event by desiccating the soil. Coauthor Prof. Arpita Mondal, Associate Professor at IIT Bombay, explained, “When the soil has moisture, some of the sun’s energy goes into evaporating that moisture rather than heating the air. But when the soil is already dry, all that energy goes directly into making the air hotter.”
This pattern underscores the cascading effects of extreme weather events, with one heatwave intensifying the impact of subsequent ones. The team emphasized the importance of understanding these mechanisms to improve forecasting accuracy and preparedness for future heat events in South Asia. Improved forecasting models could enable countries in the region to mitigate the impacts of extreme heatwaves, reducing threats to public health, agriculture, and water security.
The findings also underline the urgency of addressing the growing frequency and severity of heatwaves in South Asia, a region highly vulnerable to climate change. By enhancing predictive capabilities and taking preventive measures, the study’s insights could help policymakers and stakeholders develop strategies to protect communities from the devastating impacts of rising temperatures.
