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.

中文翻译：

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季风前纬向风北移加剧印度热浪


近几十年来，印度观察到的极端高温越来越持续。印度中北部是一个人口稠密的地区，容易出现热浪，在季风前季节经历了创纪录的最高气温（$>$48°C）。虽然研究表明气温升高导致热浪呈积极趋势，但我们发现印度中北部季风前平均日最高温度发生了变化，导致 1998 年后气温上升了 0.7°C。温度的跃升与自 1998 年以来副热带西风急流的北移有关。我们发现，副热带西风急流的经向偏移解释了印度中北部热浪特征变化的 25% 以上，这意味着 1998 年后热浪的增加与急流的北移有关。这些发现强调，印度中北部热浪的加剧是由政权更迭引发的大气动力学变化驱动的，而全球变暖进一步加剧了这种情况。