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Alarm bells over the impact of climate change have been heard in Kerala for the past few years but never so loud in the month of August, among the wettest monsoon months, as rains have kept away for so long this year as to prompt alerts of heat wave-like conditions in the southern state.
Normally it pours in August, as it did infamously in 2018, triggering what has come to be referred to as the century’s worst floods, but there appears to be no precedent where rains have kept away for a sustained period — even during an El Niño year such as this, when rains shut out over large parts of the country due to the warming of the far-off Central and East Equatorial Pacific.
Bearing the brunt
Southern and Central Kerala have bore the brunt of the heat generated by ‘sinking air motion’ — when air descends, it leads to compression, higher pressure and warming as against when air ascends, pressure lowers and cools down, leading to formation of clouds and rain. Higher pressure does not allow formation of clouds, and leads to sustained warming over time.
A heatwave is declared if the maximum temperature of a station reaches at least 40°C in the plains, at least 37°C in coastal areas and at least 30°C in hill regions; and the departure from normal is at least 4.5°C. Since Kerala is a coastal state, a departure of 4.5°C above the threshold of 37°C would be sufficient to declare a heatwave.
‘Feels-like’ temperatures
Rise in temperature accompanied by high humidity causes the heat index to inch up in tandem, causing discomfort. Humidity in stations where temperatures rose by 5°C on Wednesday ranged between 60-90 per cent. ‘Feels-like’ temperature is a measurement of how hot or cold it really feelslike outside. It relies on environmental data such as ambient air temperature, relative humidity and wind speed to determine how weather conditions feel to the bare skin.
The IMD has ruled out rains returning to Kerala over the next five days at least. Some international weather agencies expect a change in the situation in early September, when a wave of rains arrive from the Laccadive Sea and adjoining South Arabian Sea, walloping Sri Lanka and the southern parts of Kerala and Tamil Nadu, and likely lasting into the rest of the first week of the month when the South-West (June-September) monsoon starts to withdraw from the extreme North-West Rajasthan.
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