Researchers from Indian Institute of Science (IISc) have found that frequency of heatwaves accompanied by drought has increased in magnitude and in area over past three decades in India.
The increases in cocktail of drought and heatwaves were seen particularly in Maharashtra and Southern Gujarat, Karnataka, Andhra Pradesh and Central India.
Heatwaves (a prolonged period when temperatures approach record extremes) and droughts are destructive even when occurring in separate events, but their concurrence is far more serious. Both phenomena have a serious bearing on water resources, affecting agriculture and human settlements.
The conclusion was based on analysis of rainfall and temperature data of 50 years. Researchers had compared Heatwave Magnitude Index daily (HWMId) — which combines duration and magnitude of heatwaves — and Standardized Precipitation Index (SPI), which defines meteorological drought from 1951 to 1981.
In all combinations of heatwaves (3.5 and 10-day events) and drought (moderate or severe) were analysed during this period. It was found that, percentage increase in frequency was most significant in parts of Maharashtra and Southern Gujarat, Karnataka and Andhra Pradesh. The increase may be due to intricate relationship of land surface processes, soil moisture, evapo-transpiration and local climate.
The area affected b extreme of extreme incident has gone from almost nothing in 1951, to nearly 4% by 2010. Nearly 18% of country’s area on average has been facing at least three days of temperatures above 85th percentile.