Why Kerala swelters in an unprecedented heatwave

Kerala, often referred to as 'God's own country,' finds itself in the grip of an unrelenting heatwave. The mercury soared past 36 degree Celsius in the State as early as February, marking the beginning of a scorching ordeal for its residents. But the heat is just one facet of the chaos unfolding across the region. Kerala is now receiving warm night forecast, humid weather warnings and hot day alerts. Wildlife, typically confined to the depths of forests, now boldly venture into Kerala's towns. From elephants to tigers, bears, and boars, these unexpected visitors add to the sense of disarray. Meanwhile, the sea churns with unpredictable fury and waves crash against the coastline as part of the kallakadal phenomenon.

Dr MG Manoj, a scientist at the Advanced Centre for Atmospheric Radar Research in Cochin University of Science and Technology, sheds some light on the matter during his conversation with News Brake, Onmanorama's Explainer Podcast.

Hot and humid
“The India Meteorological Department has declared a heatwave in Kerala for the second time in its history. The first incident was in 2016-17 when one of the strongest El Nino phenomenon took place. It has recurred in exactly seven years,” Dr Manoj said adding that the El Nino usually recurs every 2 or 7 years.

According to the IMD, the heatwave is defined based on the temperature thresholds over a region in terms of actual temperature or its departure from normal. A heatwave is declared if the following conditions are met simultaneously for at least 2 days. One, the maximum temperature of a station reaches at least 40 degree Celsius or more for the plains and at least 30 degrees or more for hilly regions. Two, the average maximum temperatures are higher by four degrees or 4.5 degrees compared to the climatological average.

The departure of temperature from climatological averages is not the only thing to be concerned about. “Humidity amplifies the sensation of heat. Sweating is an automatic mechanism to bring down the body temperature that is controlled by our hypothalamus in the brain. While an optimal humidity cools down our body through sweating, a humidity above the ideal range of 40- 50 per cent can be harmful. Just like burns from steam is more harmful than boiling water, humidity amplifies the heat felt by the human body. This is why humidity is a part of the heat index,” says Dr Manoj. The scattered thunderstorms and the humid air in coastal towns are not helping matters either, he added.

According to Dr Manoj, the El Nino effect which is largely blamed for the early arrival of summer in the State has become neutral now. El Nino is a coupled ocean atmosphere phenomena, that is an anomalous warming in the east central Pacific close to the equator which increases the sea surface temperature (SST) by 2 to 5 degree Celsius above normal.

“We are still facing El Nino's lingering effects. Several millions of square kilometres of warming in the Pacific has an impact on the atmosphere. It affects the pressure pattern in the atmosphere and the global wind pattern. So wherever rain is received, you may not get rain at all and vice versa. In India, the wind pattern is not favourable for any rain cloud formation resulting in lack of summer rains,” he said.

But El Nino is not the only factor which is driving up temperatures in the Indian subcontinent. The presence of anticyclones in the atmosphere is not allowing the hot air from the ground to rise. “It suppresses convection over the land area so that we will feel additional warming. This is why summer arrived before the pre-monsoon months of March this year,” Dr Manoj told Onmanorama.

Global warming
Global warming is also lurking in the background as a silent accomplice .. “The air temperature and the sea surface temperatures are rising, and the global oceans are warming at an unprecedented rate. The Indian Ocean is warming at double the rate compared to the global oceans. The Arabian Sea is in a very hot state boiling state now. There is an anomalous warming of 1.5 to 2 degree Celsius along the Kerala coast,” he said. According to the CUSAT scientist, even the kallakadal phenomenon could be influenced by the heating of the oceans.

The change in land use pattern is another factor driving up the heat. The fall in the green cover which reflects heat and rise of concrete building, tarred roads etc which results in heat absorption is also a reason for the increasing temperatures. From enhancing green cover to adopting eco-friendly practices, a multi-pronged approach is required to mitigate the impacts of climate change.