India's monsoon is dependent on several factors, including conditions over the Indian Ocean, climate change, El Niño and La Niña, among others. The La Niña effect is one of the most important reasons behind changes in seasonal weather patterns of India. The periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific is referred to as the La Niña effect. La Niña causes warm water to be pushed toward Asia.
The most recent La Niña effect lasted till February 2023. This was the first "triple-dip" La Niña of the 21st century, which means that the event had been occurring continuously for three consecutive years.
Effects of triple-dip La Niña and subsequent El Niño on India’s monsoon
The triple-dip La Niña affected temperature and precipitation patterns in different parts of the world. More intense and longer rainfall in southeast Asia is associated with La Niña.
However, an El Niño year following a La Niña year is the "worst-case scenario" for monsoon deficits, because La Niña conditions usually bring above-average rainfall to India, while El Niño brings drier-than-normal conditions. As a result, the combination of the two events has a significantly negative impact on monsoon rainfall.
This year, El Niño is likely to begin in July. El Niño is the phenomenon in which trade winds weaken, as a result of which warm water is pushed back east, toward the west coast of the Americas, where the Pacific Ocean is present. Since warm water is pushed back east due to El Niño, the monsoon in India can be affected.
During the La Niña years, there was an accumulation of snowfall over Eurasia, the area of Earth comprising all of Europe and Asia.
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How snowfall accumulation over Eurasia can offset El Niño effects for India, and how this will affect the country's monsoon
Experts say that snowfall accumulation over Eurasia is likely to play a compensating role to the El Niño effect for India. This is because the accumulation of snowfall over Eurasia influences the temperature and pressure patterns over Asia. These patterns can alter the monsoon circulation. Also, heavy snowfall over Eurasia cooled the atmosphere, creating a high-pressure system. This system can strengthen monsoon winds over India.
“The accumulation of snowfall over Eurasia can play a compensating role to the El Niño effect because it influences the temperature and pressure patterns over Asia, which can alter the monsoon circulation. Heavy snowfall over Eurasia leads to the cooling of the atmosphere. It creates a high-pressure system, which strengthens the monsoon winds over India and helps to compensate for the weakening effect of El Niño,” Dr Anjal Prakash, Research Director, Bharti Institute of Public Policy, Indian School of Business and IPCC Author, told ABP Live.
Since the sea surface temperatures in the Pacific Ocean become warmer-than-normal during an El Niño event, the rainfall patterns over the Indian subcontinent are affected. When monsoon winds weaken, the amount of rainfall over India is reduced. However, accumulation of snowfall over Eurasia can strengthen the monsoon winds and increase rainfall over India.
“During an El Niño event, the sea surface temperature in the Pacific Ocean becomes warmer than normal, which can affect the atmospheric circulation and rainfall patterns over the Indian subcontinent. This can weaken the monsoon winds, reduce the amount of rainfall over India, and lead to drought-like conditions in some regions. However, heavy snowfall over Eurasia creates a high-pressure system that can counteract the weakening effect of El Niño by strengthening the monsoon winds and increasing the amount of rainfall over India,” Dr Prakash explained.
He concluded that in this way, the accumulation of snowfall over Eurasia can potentially offset the negative impact of El Niño on India’s monsoon season and help to maintain adequate rainfall over the Indian subcontinent.