Arctic warming behind surge in heat waves

Gachibowli: Heatwaves during summer have become a regular phenomenon in India, with increasing ferocity every year. April and May month have come to witness several fatalities on account of heat stress where cooling has become more of a necessity rather than luxury in the country.

Following abnormal heatwaves, thousands of deaths of humans and livestock were reported around the eastern Indian state of Odisha in 1998, Andhra Pradesh in 2003 and Ahmedabad and other parts of western Indian state of Gujarat in 2010. Even globally, the World Health Organisation (WHO) noted that more than 1.6 lakh people died due to severe heat waves during 1998-2017.

Researchers from India and Brazil recently published an article, 'Large-scale connection to Deadly Indian Heatwaves.' Recently, Arctic region is warming at an alarming rate, leading to what is called Arctic Warming.

In the Arctic region, temperature is increasing more than twice as fast as the global average. This reduces normal equator (a hot region) to pole temperature gradient.

Because normally Arctic region is very cold,decrease of temperature gradient favors decrease of zonal wind (wind from west to east, which occurs in the mid-latitudes) and its vertical shear (because of so called thermal wind relation).

A decrease of zonal wind favors some special conditions (which are becoming more frequent recently).An increase of Rossby wave amplitudes for some wavenumbers or the QRA.

The positioning of amplified Rossby waves is such that in some specific locations (over India) a high-pressure cell occurs, leading to sinking motion and increasing surface temperature drastically. This increase of surface temperature causes heat waves.

Although, this QRA mechanism is shown to be the cause of 2003 European heatwave and 2010 Pakistan flood and Russian heat wave and other extreme events affecting human and animal life, Dr V B Rao and co-authors have shown for the first time that, heatwaves leading to deaths, can occur in India, due to QRA which is caused by arctic warming which in turnis a result of global warming.

Indeed, several authors have shown that Indian heat waves are increasing, but a possible cause is global warming. Thus, there is an urgent need to plan mitigation of this very adverse climate change.

Dr V B Rao and others suggested in their article that Indian heatwaves can be predicted about 4 days in advance prior to their occurrence.

The results of this study were published in a reputed British journal, Quarterly Journal of Royal Meteorology,by Dr V B Rao, National Institute for Space Research, INPE, Brazil, Dr K KoteswaraRao (corresponding author from Azim Premji University), Dr B Mahendranath (Andhra University), Dr T V Lakshmi Kumar (SRM Institute of Science and Technology), and Govardhan Dandu (University of Hyderabad, a PhD student).