Blast from west behind heat

Hope of cooler weather lies in Mediterranean storm
Weather records over the past decades suggest that summers in India have become hotter, but scientists today linked the extreme heat in eastern India to the flow of hot and dry winds from India’s northwest.

In Calcutta today, the maximum temperature climbed down to normal at 35.9 degrees Celsius, though the higher humidity range and power cuts denied people comfort. The high humidity has triggered hopes of a Nor’wester in the next three-four days. (See Metro)

Meteorologists said respite from the heat may be expected if a type of extra-tropical storm they called a “western disturbance” originating over the Mediterranean region moved eastward over India and then southeast along the Gangetic plains.

“A western disturbance has a cooling effect, but we haven’t felt the effects of a western disturbance in northern India for a few weeks now — hot, dry air from the northwest is moving towards the east,” said B. Bandopadhyay, a scientist at the India Meteorological Department (IMD), New Delhi.

Gaya was among the hottest places in eastern India today with a temperature of 44.8 degrees Celsius — about 6 degrees Celsius above normal.

A western disturbance currently observed over Jammu and Kashmir is moving eastward over the mountains but is unlikely to cool the plains, scientists said.

The IMD said today heat wave conditions were likely to continue over the plains of northwest India over the next 24 hours, but another western disturbance was likely to move into western Himalayas around April 15. “But the effects of this one also appear set to bypass the plains,” an IMD official said.

Across wide swathes of northern and eastern India, weather instruments recorded temperatures several degrees above the long-term normal readings. Delhi’s Palam weather office recorded a maximum temperature of 42.7 degrees Celsius, about 7 degrees Celsius higher than normal, while Lucknow and Patna both recorded maximum temperatures about 4 degrees Celsius above normal.

The heat wave, meteorologists said, appears in line with research that suggests average temperatures over India have increased over the past several decades. A study by scientists at the Indian Institute of Tropical Meteorology (IITM), Pune, has indicated that the maximum as well as minimum temperatures have increased significantly, by 0.2 degree Celsius per decade, over the past three decades.

“When the mean (average temperature) shifts to a higher level, the chances of heat waves occurring also rise,” said K. Krishna Kumar, a senior scientist at the IITM. “The number of hot days also appears to be increasing,” Kumar told The Telegraph.

A recent analysis of India’s temperature trends during the pre-monsoon months of March, April and May from 1970 to 2005 shows that the frequency of hot days and nights has increased for India as a whole — although there are regional variations.

The new IITM study, published in the Journal of Earth Sciences, shows that frequency of hot days has significantly increased over the southern parts of India, but there has been no significant change over the northern parts of India.

The Centre for Science and Environment, New Delhi, today cited a three-year-old research paper by the Indian Institute of Technology, Delhi, showing regional variations in trends in maximum and minimum temperatures.

The study by S.K. Dash, an atmospheric scientist at the IIT, analysing temperatures between 1901 and 2003 suggests that in the eastern coastal region, the maximum temperature has gone up by 0.6 degree Celsius and the minimum by 0.2 degree Celsius. In northwest India, according to the study, while the maximum temperature has increased by 0.6 degree Celsius, the minimum temperature has dropped by 0.2 degree Celsius. The IMD has said March 2010 was the second warmest March since 1901.