‘Drought, heatwaves increasing in frequency’

Analysing rainfall and temperature data of 50 years, researchers from Indian Institute of Science (IISc) have found that the frequency of heatwaves accompanied by drought has increased not only in magnitude but in area too over the past three decades – particularly in Gujarat and Central India.
Heating up fast Researchers calculated the Heatwave Magnitude Index daily (HWMId) — which combines duration and magnitude of heatwaves — and the Standardized Precipitation Index (SPI), which defines meteorological drought from 1951 to 1981.
Even the extreme of extreme scenarios – of 10-day long heatwave where temperatures are above the 95th percentile of range recorded – has been found on the rise in Gujarat and mid-South India.
The longest was in 1983 when a heatwave lasted 63 days; while, in 1998, heatwave conditions affected nearly 49% of the country’s area.
While the rest of the country, too, showed increases in frequency, a surprising decrease was seen in Rajasthan and West Bengal.
Researchers believe this could be due to the intricate relationship of land surface processes, soil moisture, evapo-transpiration and local climate.
The area affected by the ‘extreme of extreme’ incident has gone from almost nothing in 1951, to nearly 4% by 2010.
Ms. Sharma said the next step would be to factor in soil moisture along with the data to develop models that could predict where the extreme events could occur.
This could contribute to policy making and ensure preparedness,” she said.
Both phenomena have a serious bearing on water resources, affecting agriculture and human settlements.

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