How does the India Meteorological Department define heatwaves?
According to the IMD, the definition of a heatwave depends on the physiography of regions.
The IMD will declare a heatwave if the maximum temperature recorded at a station is 40 degrees Celsius or more in the plains, 37 degrees Celsius or more in the coast, and 30 degrees Celsius or more in the hills
A heatwave’s severity is determined by its departure from normal temperature.
There is a ‘normal heatwave’ when the departure is by 4.5-6.4 degrees Celsius and a ‘severe heatwave’ if the departure is greater.
Heatwave declaration could also be based on actual maximum temperature: a ‘heatwave’ is when this figure is greater than 45 degrees Celsius and a ‘severe heatwave’ when greater than 47 degrees Celsius
The IMD takes this only when at least two stations in a meteorological subdivision report such a high maximum or when at least one station has recorded a corresponding departure from the normal for at least two consecutive days
Heat Action Plans (HAPs)
With the severity and frequency of heatwaves increasing across the country, governments at various levels — State, district, and city — have prepared heat action plans (HAPs).
HAPs aim to increase preparedness and lower the adverse impacts of extreme heat by outlining strategies and measures to prepare for, address, and recover from heatwaves.
What do the HAPs recommend?
HAPs typically suggest a combination of measures such as using forecasts and early warning systems to alert the public and relevant authorities about heatwaves, educating the public through campaigns that provide information on risks associated with heatwaves, building heat shelters and cooling centres, and providing clean drinking water to avoid dehydration.
HAPs provide directives for hospitals to be well equipped with supplies and an adequate number of trained healthcare workers to recognise and treat a large influx of patients with heat-related illnesses.
HAPs also suggest long-term measures such as adopting urban planning strategies that promote tree planting, using heat-resistant building materials to reduce urban heat island effect, and using cool roofing technologies to reduce solar absorption, thereby decreasing indoor temperatures.
Special interventions for vulnerable communities during a heatwave
All HAPs prioritise the protection of vulnerable populations such as low-income communities, children, and the elderly.
For the targeted interventions are needed that account for the varying needs of populations based on local social and demographic factors, in addition to infrastructure elements that could exacerbate heat.
Regional variations and socio-economic differences
Over 90% of India’s economy is informal and starkly visible, be it a pushcart vendor, a chaiwala, household help, or sanitation worker.
If we acknowledge heatwaves as a public health concern, targeted strategies need to be formulated by recognising various socio-economic differences.
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