The increasing frequency of extreme Heat Waves (HWs) has generated significant societal impacts in recent years. This study used different observational datasets to investigate the HW characteristics over India during the post-El Niño spring and early summer seasons (April to June; AMJ). Analysis suggests that HW days are more prevalent over India, predominantly increased in south-central and northwest India, during the decaying phase of strong El Niño years. It is found that anomalous anticyclone circulation accompanied by high pressure extending from the Western North Pacific region towards the Bay of Bengal and India is responsible for enhanced HW days and intensity during the AMJ of strong El Niño decay years. This anomalous anticyclone-induced downdraft reduces the specific humidity in the lower troposphere, leading to decreased cloud cover over India. As a result, shortwave radiation is enhanced at the surface, which causes abnormal HWs over India. During the decaying phase of strong El Niño years, the HW days over India contributed to an increase in the frequency of Discomfort Index hours (above 28 °C), maximum temperatures exceeding 40 °C (hours per day), and Universal Thermal Climate Index days above 38 °C and 46 °C during the spring and early summer months, especially in the East Coast, central, and northwestern parts of India. Thus, proper prediction of large-scale atmospheric circulation over the Indo-western Pacific region during El Niño can help to predict the HW conditions three months in advance. This would help to implement suitable adaptation measures and put into practice strong mitigation policies to limit the increased risk of such events during AMJ of El Niño decay years.

中文翻译：

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厄尔尼诺现象过后的春季和初夏期间印度上空的热浪频率增加


近年来，极端热浪（HW）频率的增加产生了重大的社会影响。本研究使用不同的观测数据集来调查厄尔尼诺现象发生后的春季和初夏季节（4 月至 6 月；AMJ）期间印度的 HW 特征。分析表明，在强厄尔尼诺年的衰减阶段，印度的 HW 日更为普遍，主要是印度中南部和西北部的增加。研究发现，从西北太平洋地区向孟加拉湾和印度延伸的伴随着高压的反气旋异常环流是强厄尔尼诺衰变年AMJ期间HW日数和强度增加的原因。这种反气旋引起的异常下降气流降低了对流层下部的比湿度，导致印度上空的云量减少。结果，地表短波辐射增强，导致印度上空出现异常的热波。在强厄尔尼诺年的衰减阶段，印度上空的高温天气导致不适指数小时（高于 28 °C）、最高气温超过 40 °C（每天的小时数）和通用热气候指数的频率增加春季和初夏期间，气温超过 38°C 和 46°C 的天数，特别是在印度东海岸、中部和西北部地区。因此，正确预测厄尔尼诺期间印度-西太平洋地区大范围大气环流有助于提前三个月预测HW状况。这将有助于实施适当的适应措施，并实施强有力的缓解政策，以限制厄尔尼诺衰退年份 AMJ 此类事件风险的增加。