Delhi at 45, Barmer at 47.5. What exactly is behind this scorching heat wave over north and central India?
North and central India is sizzling with day temperatures around 45 degrees. While Delhi recorded around 45 degrees, the desert town Barmer recorded 47.5 degrees Celsius.
If this wasn't bad enough, the Met department has predicted the heat wave will stay in the region for another ten days.
It's hard to pinpoint a single conclusive reason, but experts say that a range of factors have caused this. These include the hot winds from Northwest India, Pakistan and Afghanistan, the depression in South India, as well as warming in the Atlantic Ocean.
The department has said that the heat wave will persist till 26 May, and then subside.
In the region surrounding Delhi, maximum temperatures were 3.1 to 5 degrees above normal, according to the Met department.
What is a heat wave?
A heat wave is declared when the maximum temperatures are found to be 4.6 to 6.4 degrees above normal. When it is beyond 6.5 degrees, the met department calls it a severe heat wave. Alternately, it uses absolute measures for heat waves, such as when temperatures cross 45 degrees. Either way, it has to be at least above 30 degrees in the hills and 40 degrees in the plains.
Reasons behind the heat wave
The current heat wave has occurred because there are clear skies and the lack of any 'weather system' has opened the doors to hot winds from the northwest, said Akshay Deoras, a Nagpur-based independent weather forecaster.
Instead, the depression over the Bay of Bengal - causing heavy rainfall in South India - is making it worse here.
"At present there is an increase in the wind speed of these north-westerly winds over Northern and Central India. This is due to the depression over the Bay of Bengal near Tamil Nadu coast," Deoras said.
The depression is also preventing humid winds from the south and east from coming to the north, making the heat wave worse for the citizens.
"The current heat wave has low humidity, because of which there is no scope for relief from pre-monsoon showers," said Mahesh Palawat, chief meteorologist at SkyMet India.
This is because humidity gets concentrated in weather systems in the Arabian Sea or Bay of Bengal, such as the one now. But once the depression dissipates in the next few days, the humidity will be back in Delhi.
"When the humidity rises with the arrival of these winds, thundershowers may commence. However relief will be limited since such pre-monsoon showers are not very widespread and do not last long,: Palawat added.
A recent study said heat waves in north and central India may have causes in the Atlantic Ocean. Titled 'Anatomy of Indian heatwaves', the paper found that the rising instances of heat waves over central and north India could be because of a weather phenomenon over the Atlantic ocean, known as 'blocking'. The study, which uses data from heat waves in the March-June months from 1982 to 2013, is co-authored by M Rajeevan, secretary, Ministry of Earth Sciences..
The present heat wave comes at a time when the planet itself is seeing record-breaking temperatures. April was the seventh straight month of record high temperatures, caused in part by the El Nino effect and global warming. April was also the third consecutive month when temperatures were higher by the largest ever margin.
Edited by Sahil Bhalla
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