Explained: Why mercury is rising and what's behind searing heatwave in March this year

New Delhi: Several parts of India have been reeling under early summer heat with the maximum temperature settling at over 35 degrees in various cities. The summer heat has set in across the country with mercury levels showing a continuous rising trend.

On Saturday (March 19), the maximum temperature recorded by the India Meteorological Department (IMD) in Delhi was 36.6 degrees Celsius, which was six notches above normal. In Madhya Pradesh, the highest temperature was recorded at 43 degrees Celsius on Friday and in Odisha, the mercury had touched 41 degrees Celsius the same day for the first time this summer.

This week, the maximum temperatures even in the Himalayan states and foothills was higher than normal.

Why mercury is rising and what's behind searing heatwave in March this year

As the sun marches northwards and according to the climatology, the month of March is when the region extending from Maharashtra to Odisha is a heat zone. In its March to May seasonal forecast issued on March 1, the IMD had already predicted that it was expecting above normal maximum temperatures most likely over many parts of western and central India and hence a heatwave can be expected extending from south Gujarat to Maharashtra to Odisha.

On the reasons for the heatwave, IMD Director General, Mrutyunjay Mohapatra has said that the higher than normal temperatures are because of the wind flow pattern in these areas. 

"The lower-level winds in these areas are from the south towards the north and that brings hotter air from land (as against when north to south winds bring colder air," he said.

The winds are southeasterly over the southern peninsular area, mainly Karnataka, Telangana with some feeble circulation which is favouring the advent of heat from south to north Tamil Nadu, Telangana, Karnataka and up to Vidarbha area of Maharashtra.

Mohapatra said, even for Saurashtra, Kutch and Rajasthan, the reason for heatwave conditions is southerly winds.

Meanwhile, meteorologists believe that the summer is going to be hotter this year as per global parameters used for gauging climatic conditions.

As oceans warm, marine cold spells are disappearing

A new study has revealed that as the atmosphere and oceans warm, marine cold spells are becoming less intense and less frequent.

According to a study published in 'American Geophysical Union', today, the oceans experience just 25 per cent of the number of cold spell days they did in the 1980s, and cold spells are about 15 per cent less intense. 

The researchers found that over the past decade, cold spells have occurred roughly 10 days per year globally, a notable drop from about 40 days per year in 1985. 

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