Heatwaves in India

Heat waves form when high pressure aloft (from 10,000–25,000 feet (3,000–7,600 metres)) strengthens and remains over a region for several days up to several weeks. This is common in summer (in both Northern and Southern Hemispheres) as the jet stream 'follows the sun'. On the equator side of the jet stream, in the upper layers of the atmosphere, is the high pressure area.
 Heat waves are the most lethal type of weather phenomenon, overall.Since the heat waves have a serious effect on human mortality, root causes of these heatwaves need to be clarified.There has been a number of mega heatwaves in recent years worldwide.India suffers from major heatwaves during March-June. The rising trend of number of intense heatwaves in recent decades has been vaguely attributed to global warming. 
Recent studies suggest that frequency, duration and intensity of heat wave events are increasing over land regions across the globe. Over India, in the past, heat waves have caused more deaths than any other natural hazard. In May 2015, a severe heat wave affected parts of southeastern parts of India (Telangana and Andhra Pradesh) which claimed lives of more than 2500 people. This was an unprecedented event caused due to persisting anomalous atmospheric conditions due to delayed onset of southwest monsoon.The present study has brought out the salient features of variability of heat waves over India and associated physical mechanisms and influence of coupled climate modes. The past observations of heat waves (1961–2013) clearly suggest a statistically significant increase in frequency, duration and maximum length of duration of heat waves over India.


This article was originally published in Nature. 

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