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La Niña, a phase of the El Niño Southern Oscillation (ENSO), occurs when the Pacific Ocean region between Indonesia and South America is cooler than usual. This phenomenon influences global weather patterns, including those in India. Here’s how La Niña specifically affects India’s climate:

Monsoon Rainfall:

• La Niña typically results in normal to above-normal rainfall during the monsoon season in India. This is due to the cooling of sea surface temperatures in the central Pacific, which affects atmospheric circulation and strengthens the monsoon winds.
• In contrast, El Niño usually brings below-average rainfall and droughts to India, leading to agricultural stress.
• Recent La Niña years (2020-2022) saw above-normal monsoon rains, which benefited agricultural productivity, while the El Niño year of 2023 resulted in below-normal rains, impacting water availability and agriculture.

Winter Temperatures:

• During La Niña, winter temperatures in India are generally colder in the north, with cooler nights but relatively warmer days compared to El Niño winters. The planetary boundary layer height (PBLH) tends to be lower, trapping pollutants close to the surface. However, higher wind speeds during La Niña help to disperse air pollution, improving air quality.
• South India may experience colder-than-usual winters during La Niña, but current meteorological data suggests the ongoing winter in India is not strongly influenced by La Niña, as its expected onset has been delayed.

Impact on Summer Heat:

• La Niña generally provides relief from extreme summer heat, as it reduces the frequency and intensity of heatwaves. In contrast, El Niño summers are typically hotter and bring record-breaking heat waves.
• For example, April 2023 saw intense heatwaves across India, attributed to the El Niño phase, but if a La Niña forms and persists into the summer of 2025, it could help moderate the extreme heat.

The "Triple Dip" La Niña Phenomenon:

• A Triple Dip La Niña refers to a rare occurrence where three consecutive La Niña events happen, as was the case from 2020 to 2022. This is significant because these prolonged events can lead to stronger climatic impacts. In contrast, the current El Niño (2023) follows this period, potentially contributing to an irregular transition between La Niña and El Niño phases, which may intensify extreme weather patterns.

Global Climate Changes and La Niña:

• Climate change is believed to be increasing the frequency and intensity of both La Niña and El Niño events. Rising sea and land temperatures are disrupting the balance of the Pacific Ocean and could exacerbate extreme La Niña events, which might lead to harsher winters in India and other regions.

Forecast for 2024-2025:

• As of December 2024, the India Meteorological Department (IMD) and global meteorological bodies predict a weak La Niña event to emerge by late 2024 or early 2025. This could lead to colder winters and above-normal rainfall in the 2025 monsoon season, offering some relief from the heatwaves and dry conditions of the previous years.

Conclusion:

If a La Niña forms by the end of 2024, it is likely to bring cooler winters, a relief from extreme summer heat, and above-normal monsoon rainfall in 2025. Given the delayed onset and weakening of the current La Niña, the overall impact on India’s climate in the immediate future might be milder compared to previous La Niña years, but it still holds potential for more favorable conditions for agriculture and air quality.