The heat wave that people of North-coastal Andhra Pradesh have been experiencing in the last couple of days has a direct link to the phenomenon of global warming. The heat wave condition is due to the blowing of dry, hot, and low northerly winds in the last couple of days.

While districts such as Guntur and Krishna have being experiencing a significantly high temperature, which is above the normal by six to seven degree Celsius, in Visakhapatnam it is two to three degree Celsius more than the normal.

The temperature in the city touched 38 degree Celsius on Monday (35 degree C is the normal) and it touched 40 degree Celsius two days ago.

Director of the Cyclone Warning Centre V.L. Prasada Rao told The Hindu that though there was no significant rise in temperature over the last couple of years, the hot wind that was blowing across, even during night time, was a recent trend. “It is mainly because of the weakening and oscillation of the low pressure troughs over the region,” he says.

The formation of low pressure troughs over the regions of Chhattisgarh, Vidarbha, and Odisha during the months of March, April, and May has been a common feature since decades.

Convergence of winds

“Troughs that are formed due to the convergence of winds from various direction cause low pressure area and, in turn, it cools the atmosphere. But this year, both the lower and the upper troughs are being weakened, as the troughs are not getting the required support from the bay region,” says the weatherman.

This year, the activity or the system over the Bay (Bay of Bengal) has been very stable and the stability is directly attributed to global warming. “Stability is not conducive for producing low pressure regions. We need instable activity,” says Mr. Prasada Rao.

Simplifying the stable and instable factors, he says, “The temperature of water and over the sea surface is much higher when compared to the normal, and that is why water vapour is unable to rise to the required level (convergence level) to form a depression. The rise in temperature in and over the bay is due to global warming,” he says.

The Director of the CWC says the heat wave condition is a temporary phenomenon and is likely to dissipate shortly, as the South-westerly monsoon is expected to touch the Kerala coast within a week.

And, in all probability, the monsoon will hit North-coastal Andhra Pradesh by mid June. “The monsoon has already arrived at the Andaman and Nicobar Islands, and we can expect a fairly normal one here also,” he says.

The activity in and over the bay is the triggering factor for the development of low pressure, which leads to depression and heavy rain. The change over the sea surface due to global warming is the key factor for the climate change.