This year (2018), even before the summers had begun, the India Meteorological Department warned the districts of Raigad, Ratnagiri and Mumbai in Maharashtra about heatwave-like conditions. Temperatures in these districts are expected to touch 38°C. This is 6°C above the normal temperature for the summer months.
Farmers and daily wage labourers are the worst-hit from heatwaves because their profession demands them to work in the sun for most part of the day. From causing crop failures to power outages, heatwaves can wreak havoc. And this is not something we are experiencing only in India. Across the globe, hot days are getting hotter and more frequent, while cold days are becoming fewer.
Come summer and newspapers and TV channels will be full of headlines, like “Beware of heat waves in coming days as high pressure forms over the area” or “Expect rain in next two three days as a low pressure system approaches”. Ever wondered why high pressure is generally associated with hotter days while low pressure is generally associated with pleasant weather? What is this high and low pressure?
The motion of air in the atmosphere above our heads plays a large part in the weather we experience at Earth’s surface. Basically, air cools as it rises, which can cause water vapour in the air to condense into liquid water droplets, sometimes forming clouds and causing precipitation.
On the other hand, sinking air is associated with warming and drying conditions. So the first important point to keep in mind is rising air equals moistening and sinking air equals drying.
Due to the Earth’s rotation and temperature gradients between poles and equator, certain places receive more sunlight, making the air in those areas hotter than the other areas.
The hot air in these areas swirl in a downward pattern, creating a high pressure system that forces the air downwards and prevents air near the ground from rising. This trapped air inside the high pressure system leads to the formation of heatwaves.
With a clear rise in intensity and frequency of heatwaves in recent years, the number of people exposed to extreme heat in India is likely to increase 18-200 times by the end of this century.
India must consider adaptation measures such as increased provision of shelter, more cooling systems and developing emergency public services to cope with problems associated with heatwave. But the key to solve this problem is to reduce global temperature.
Chief Cartoonist, Down to Earth, and Supplement Editor, Gobar Times (2016-2021)