Click it and Unblock the Notifications
In 2022, South Asia, including India and Pakistan, witnessed an unusual surge in temperatures during March and April, where the mercury soared 3-8 degrees Celsius above the usual, marking an extended phase of heatwaves. These extraordinary weather conditions have been closely analyzed in a study by researchers from the Indian Institute of Technology Bombay and Germany's Johannes Gutenberg-University Mainz. Their research, featured in the Journal of Geophysical Research: Atmospheres, unveils a concerning trend where one heatwave might set the stage for another, potentially leading to a series of intense, back-to-back heatwaves.
The study pinpoints a significant factor contributing to this cycle: the excessive dryness of soil following an initial heatwave. When the soil loses its moisture, subsequent heatwaves become more severe due to a lack of evaporative cooling, which ordinarily helps to moderate air temperatures. "But when the soil is already dry, all that energy goes straight into making the air hotter," explained co-author Arpita Mondal, an associate professor at IIT Bombay. This finding underscores a critical shift in how heatwaves can self-propagate under certain conditions.
March and April's heatwaves were each triggered by distinct atmospheric phenomena. The research team discovered that the earlier heatwave in March was mainly attributed to a sudden increase in atmospheric Rossby waves' amplitude, which are large-scale meanders in high-altitude winds. "The waves grew stronger as high-altitude westerly winds near the poles (extratropical jet stream) transferred energy to westerly winds closer to the equator (subtropical jet stream) as they came closer during the heatwave," lead author Roshan Jha from IIT Bombay elaborated. Conversely, the April heatwave was primarily induced by the arid soil conditions left in the wake of the previous month's heatwave, facilitating a heat transfer to India from the northwestern land areas of Pakistan and Afghanistan.
Link Between Heatwaves and Climate Change
The study also draws attention to the broader implications of these findings in the context of climate change. The heat events of March and April 2022 had a one in 100 years probability of occurrence, but climate change has escalated their likelihood by thirtyfold, as indicated by an attribution study published in 2023 in the Environmental Research Climate journal. Subimal Ghosh, an institute chair professor at IIT Bombay, emphasized the importance of recognizing how wind patterns are evolving in a warming world. "Understanding these mechanisms is crucial for improving our ability to forecast and prepare for extreme heat events in South Asia," Ghosh remarked, pointing to the need for enhanced preparedness and mitigation strategies to combat future heatwaves.
The interplay between atmospheric processes and the onset of heatwaves suggests that early heat in March can deplete soil moisture, setting a precedent for heightened temperatures in subsequent weeks. "Our findings indicate that waveguide interaction together with equatorward energy transfer drives early heat in March, subsequently setting the stage for further heat in the following weeks by depleting soil moisture levels," the authors noted. This cycle, propelled by the dryness of the soil and atmospheric conditions, highlights the intricate dynamics of climate systems and the escalating challenges posed by climate change.
In summary, this research underscores a vicious cycle where one heatwave exacerbates the conditions for another, through soil dryness and atmospheric changes. With the backdrop of climate change making such extreme heat events more probable, understanding and predicting these patterns become crucial for future preparedness. The analysis not only sheds light on the specific drivers behind the heatwaves of 2022 but also signals the need for heightened awareness and action in the face of an increasingly warm future.
