IMD to release weather-wise hazard score for each state

As instances of intense heatwaves increase across the country, the India Meteorological Department will in May or June release hazard scores in all states on different weather parameters that lead to or aggravate extreme heat. This is expected to help in heatwave management.

A heat hazard analysis will be an annual exercise carried out by the weather bureau between March and June, when temperatures soar in various parts of the country, a Met official aware of the project details said, declining to be named. This analysis takes into account a host of parameters such as maximum and minimum temperatures, humidity, wind and duration of heatwave to release a score for each state.

“These scores could be used in the future for setting thresholds to generate heatwave impact-based alerts for specific locations,” the official said. “Most work around the project has been completed and we are hoping to release this by mid-May or June this year.”

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Although India sees high temperatures between March and June, temperature recordings from some parts of the country have shown sharp spikes over the past decade. Recently, over 13 people died of heat stroke at an award function in Navi Mumbai, making it one of the highest death tolls from a single heatwave incident in the country’s recent history.

There were 706 heatwaves between 1971 and 2019, according to a study published in 2021 by former earth sciences secretary M Rajeevan and weather scientists Kamaljit Ray, SS Ray, RK Giri and AP Dimri.

Explaining how hazard scores will be issued for the heat hazard analysis for states, the official said that graded weightage will be given based on each weather parameter. For instance, the weight of one is given to each day when maximum temperatures are above normal, a weight of two is given when maximum temperatures of a day meet the Met departments heatwave criterion, and a weight of three is given when maximum temperature of a day meets its severe heatwave criterion.

These scores are then aggregated for each month from March to June for each weather station, and average daily scores for each month are calculated, he said. The same exercise will be repeated for each of the weather parameter, including minimum temperature, relative humidity, wind speed and duration of heat spell.

“In our recent experiences, we have learnt that maximum temperatures are not the sole criterion for heat analysis. We have to take into consideration other factors as well,” the official said. “This project will help future studies and also help governments and agencies take timely and appropriate action for heatwave management during the peak season.”