Context: Recently, the Meteorological Department (IMD) issued heatwave warnings, urging caution, as Delhi reached a record-breaking temperature of 52.3 degrees Celsius.

Heatwave

• Meaning: It is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India. 
• Conditions for Declaring a Heatwave: When the temperature exceeds 40°C in the plains or 37°C in coastal regions.

o if the temperature is 4.5°C above the normal temperature.

• Duration and Consistency: The declaration requires at least two consecutive days of these extreme temperatures.
• At least two weather stations in a sub-division must record such temperatures.
• Severe Heatwave Criteria: The temperature must exceed the normal by 6°C.
• Causes:

o El Nino's Influence: One significant factor contributing to heatwaves is the El Nino weather pattern, characterized by abnormal warming of waters in the equatorial Pacific Ocean.

o High-Pressure Systems: Another factor contributing to heatwaves is the presence of high-pressure systems over the Southern peninsula and South-Eastern coastal areas.

o Atmospheric Dynamics: These high-pressure systems push warm air closer to the Earth's surface, intensifying heat levels and hindering the incoming sea breeze that typically cools the land.

o Cumulative Effects: The combined influence of El Nino and high-pressure systems creates a potent environment conducive to prolonged heatwaves and extreme heat events.

• Duration of heatwaves: Earlier, heatwaves used to last four to eight days.

o In the last two years alone, India has seen an unprecedented 328 heatwave days.

o 2023 was the hottest year on record.

• India’s Initiative: India’s first heatwave action plan was developed three years after a heatwave claimed 800 lives in Ahmedabad in May 2010. 

o It involved setting up an early warning system, improving the healthcare system and creating awareness.