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Heatwaves to intensify in India from next year: Study

, TNN|
May 18, 2019, 10.42 AM IST
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The IMD has issued a heat-wave forecast for several locations in India for the next few days.

Highlights

  • A study by the Indian Institute of Tropical Meteorology said “El Nino Modoki”, a weather system different from El Nino, could be responsible for the increase in heat waves in India
  • Depletion of soil moisture and transfer of heat from the earth to the atmosphere would also trigger them.
PUNE: The frequency of heat waves and their duration in India may begin to increase from as early as 2020, says a study by the Indian Institute of Tropical Meteorology (IITM).

The study said “El Nino Modoki”, a weather system different from El Nino, could be responsible for the increase in heat waves in India. Depletion of soil moisture and transfer of heat from the earth to the atmosphere would also trigger them.

These events are likely to happen between 2020 and 2064, affecting parts of southern India and coastal regions that have till now largely escaped heat waves.

The study, called “Future Projections of Heat Waves Over India from CMIP5 Models” and published in the international journal “Climate Dynamics”, examined nine climate models to understand how the frequency, intensity and duration of heat waves in India will increase and its severe and adverse impact on health.

The models used in the study identified 54 heat-wave events in India between 1961 and 2005. This number is likely to go up with the probability of 138 heat-wave events between 2020 and 2064.

Past studies show that the variability of heat waves in India is linked to El Nino and Indian Ocean sea-surface anomalies, P Mukhopadhyay, a scientist at IITM who conducted the study, told TOI.

el nino info

“The studies suggest that frequency, duration and spatial extent of heat waves over India are found to be more in the succeeding year of El Nino where the eastern Pacific Ocean warms up. However, a stronger relationship is emerging from the central and western parts of the equatorial Pacific. El Nino Modoki events, where the central Pacific ocean warms up, may be responsible for the prolonged and more frequent heat waves in India,” the paper said.

The findings also showed that one heat-wave event has occurred over northwest India and southeast India per season, with an average duration of about 5-7 days, between 1961 and 2005.

“Future projections suggest an increase in heat-wave frequency and duration across the country from 2020. The models used for the study suggested an increase of 1.5-2.5 heat-wave events, with an increase of 12-18 days on an average between 2020 and 2064. This is a noticeable increase but is subject to model projection uncertainties in both the heat-wave events and heat-wave days,” Mukhopadhyay added.

Atmospheric conditions during heat-wave events over northwest India are associated with depleted soil moisture, he added.

“The lack of soil moisture causes reduced evapotranspiration, a process by which water is transferred from the land to the atmosphere by evaporation. This can increase the possibility of more heat being transferred from the earth to the atmosphere, creating a warmer environment. This situation could also happen in coastal regions which are generally cooler than inland areas. Planting more trees, which maintain soil moisture, cause more evapotranspiration and help in latent cooling, is a way out,” Mukhopadhyay said.

‘Similar, But Different’

During an El Nino pattern, the eastern Pacific Ocean is warmer than the central and western Pacific Ocean.

In an El Nino Modoki event, the central part of the Pacific ocean warms more with cooling in the eastern and western parts.

It is possibly the first time that research has connected future heat waves in India with El Nino Modoki events

Other findings

Heat-wave duration will rise by 0.5 events per decade and by 4-7 days per decade over central and northwest India

Increase of about two heat waves and increase of 12-18 days in heat-wave duration between 2020 and 2064

The Weather, This Year

A heat wave gripped several parts of the country in March and April this year. The maximum day temperature for March broke records in at least six locations in Maharashtra — Pune, Mahabaleshwar, Satara, Malegaon, Solapur, Nashik and Aurangabad — on March 29, 201. It prompted a heat-wave alert for parts of the state. In the last week of April, a Skymet Weather Services report spoke of a continuous heat build-up across the country with parts of Vidarbha, Marathwada, Maharashtra, Uttar Pradesh, Delhi, Rajasthan, Gujarat, Odisha and Telangana experiencing heat-wave conditions.

IMD’s Forecast

The IMD has issued a heat-wave forecast for several locations in India for the next few days, including some parts of Vidarbha and isolated pockets over Chhattisgarh, coastal Andhra Pradesh, Rayalaseema, north interior Karnataka and Telangana.

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