Northward Shift of Pre‐Monsoon Zonal Winds Exacerbating Heatwaves Over India

Abstract

Abstract India has observed increasingly persistent heat extremes in recent decades. North‐Central India, a highly populated region prone to heatwaves, has experienced record maximum temperatures (>48°C) during the pre‐monsoon season. While studies have shown positive trends in heatwaves due to rising air temperature, we identify a shift in pre‐monsoon mean daily maximum temperature over North‐Central India, resulting in an increase in temperature by 0.7°C post‐1998. The jump in temperature is associated with a northward migration of the subtropical westerly jet since 1998. We find that the meridional shift in the subtropical westerly jet explains more than 25% of the variability in heatwave characteristics over North‐Central India, implying that the increase in heatwaves post‐1998 is associated with a northward shift of the jet. These findings highlight that the exacerbation of heatwaves in North‐Central India is driven by atmospheric dynamical changes triggered by a regime shift, further compounded by global warming.

Keywords

• heatwaves
• India
• regime shift
• subtropical westerly jet
• pre‐monsoon season
• northward shift