Context:
Throughout April, India witnessed an unusual frequency of heatwave conditions, as noted by the India Meteorological Department (IMD).
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- In April, either small pockets or considerably large geographical areas grappled with heatwave conditions.
- Although the southern peninsular and southeastern coastal regions have been worst affected by the heat waves, the northern plains have not yet encountered such conditions this season.
- The IPCC (The Intergovernmental Panel on Climate Change) and weather models show a significant shift in India’s heatwave patterns especially in the southern peninsula.
Conditions to declare heatwaves
- IMD announces a heatwave when the maximum temperature recorded in at least two locations across the plains reaches 40 degrees Celsius or surpasses 4.5 degrees Celsius above the normal.
- In hilly areas, a heatwave is declared when temperatures exceed 30 degrees Celsius.
- While in coastal regions, it’s declared at 37 degrees Celsius.
- Irrespective of the area, a severe heatwave is declared if the temperature departure exceeds 6 degrees Celsius from the normal.
Factors Behind April Extreme Heatwave
El Nino Impact: The year 2024, began under the influence of El Nino, it is a weather pattern, that refers to an abnormal warming of surface waters in the equatorial Pacific Ocean, which leads to extreme heat in many parts of the world and the ocean.
- Anticyclone Systems Influence: The consistent presence of anticyclone systems over the southern peninsular and southeastern coastal areas also contributed to the intense heat observed in April.
- These high-pressure systems force air downward toward the Earth, causing air subsidence and generating additional surface heat.
- Additionally, these anticyclone systems disrupt the normal sea-to-land breeze flow (incoming cooler sea breezes) that is responsible for cooling down the land frequently.
- Combined Influence: The combined impact of El Nino and anticyclone systems resulted in exceptionally hot conditions and widespread heatwaves during April.
- Notably worst affecting regions were: – Gangetic West Bengal, Odisha, Andhra Pradesh, Telangana, Tamil Nadu, Kerala, Karnataka, and Maharashtra.
Regions prone to heatwaves
- The Core Heatwave Zone (CHZ), which includes central, northern, and peninsular India from Gujarat to West Bengal, experiences heatwave conditions annually during the summer season from March to June, occasionally extending into July.
- The fact that Sikkim and Kerala have been added to the list of territories impacted by heatwaves suggests that summertime temperatures outside of the CHZ are growing quickly.