Northward Shift In Summer Winds Worsening Heatwaves In North-Central India, IIT Bombay Study Reveals

Mumbai: A study led by the Centre for Climate Studies at the Indian Institute of Technology Bombay (IITB) reported that the northward shift in summer winds is worsening heatwaves over North-Central India. The study revealed that this shift, which occurred after 1998, is responsible for 25% of the observed variations in frequency, duration, and total cumulative heat in summer heatwaves in the region. 

North-Central India, where millions of people live, often faces dangerous heatwaves in the months before the monsoon. While scientists have known that global warming is making these heatwaves worse, this new study shows that changing wind patterns high in the atmosphere are also playing a big role. 

The research titled "Northward shift of pre-monsoon zonal winds exacerbating heatwaves over India" suggested that this change in wind patterns is likely due to a jump in Pacific Ocean temperatures that happened around 1998, possibly made worse by global warming.

Roshan Jha of IITB, the lead author of the study, said, "We founds̄ that since 1998, the temperature over North-Central India has increased by about 0.7°C during the pre-monsoon summer season. This increase appears to be due to the northward movement of the band of strong upper tropospheric winds, known as the subtropical westerly jet."

"This change in high-altitude wind patterns is making heatwaves happen twice more often as compared to pre-1998, with more than double cumulative heat during the heat wave. This is really worrying for the large populations who live in this area,” added Arpita Mondal, Associate Professor at IIT Bombay and one of the study's authors.

“This change isn't just affecting India, but it's also affecting nearby areas like Pakistan and the Middle East,” said Jha, who is a PhD student at Centre for Climate Studies. “Our research shows how important it is to understand changes in wind patterns. These changes, whether they're natural or caused by climate change, are making heatwaves worse in this region," he added.

The research team used multiple datasets, including station-based temperature observations of the India Meteorological Department (IMD) and state-of-art globally assimilated data of weather variables from the European Center for Medium Range Weather Forecasts (ECMWF) Reanalysis from 1973 to 2022. These findings can inform operational forecasts and long-term projections of heat waves. If these patterns are represented well in computer-based climate models, the heat wave prediction will be more accurate, aiding in heat action plans.