The Assumed Connection
For decades, the forecast has seemed simple: when El Niño arrives, India's monsoon suffers. Historically, there is a strong basis for this concern. An El Niño event, which involves the unusual warming of surface waters in the central and eastern Pacific
Ocean, tends to disrupt global weather patterns. For India, this disruption often manifests as weaker monsoon winds and reduced rainfall. Many of India's most severe drought years have coincided with strong El Niño events, establishing a clear correlation in the minds of farmers, economists, and the public alike. This connection is so established that the mere forecast of an El Niño can cause jitters in the agricultural sector and stock markets, long before the first clouds of the season gather.
How El Niño Disrupts the Monsoon
To understand the link, we need to look at a massive atmospheric engine called the Walker Circulation. Under normal conditions, strong trade winds blow from east to west across the Pacific, piling up warm water in the western Pacific near Asia and Australia. This warm, moist air rises, creating a low-pressure system that fuels rainfall, and is part of the larger circulation that helps draw monsoon winds towards India. During an El Niño, these trade winds weaken or even reverse. The pool of warm water sloshes eastward, away from Asia. This shifts the area of rising air, weakening the low-pressure system that helps drive the monsoon. The result is often descending, drier air over the Indian subcontinent, suppressing the vital rainfall the country depends on.
The Indian Ocean's Counter-Move
Here is where the story gets interesting. The Pacific Ocean isn't the only player. India's weather is also profoundly influenced by its own backyard: the Indian Ocean. A phenomenon known as the Indian Ocean Dipole (IOD), sometimes called the 'Indian El Niño', can act as a powerful counterweight. The IOD measures the temperature difference between the western Indian Ocean (near the Arabian Sea) and the eastern Indian Ocean (near Indonesia). When the IOD is in a 'positive' phase, the western Indian Ocean becomes warmer than the eastern part. This warmer water in the Arabian Sea increases evaporation and strengthens the moisture-laden winds blowing toward India, effectively giving the monsoon a helpful push.
When a Positive IOD Saves the Day
A strong positive IOD can significantly offset, and sometimes even completely neutralise, the negative impact of an El Niño. By creating a localised low-pressure zone and boosting moisture supply from the Arabian Sea, it can counteract the drying effect originating from the Pacific. History provides compelling examples. The year 1997 witnessed a 'super' El Niño, one of the strongest on record, yet India received normal to above-average rainfall. The reason was an exceptionally strong positive IOD that developed concurrently, saving the monsoon from what could have been a catastrophic failure. More recently, in 2019, a positive IOD helped deliver surplus rainfall despite the presence of a weak El Niño. These instances prove that an El Niño year does not automatically sentence India to a drought.
Other Influential Factors
Beyond the IOD, other elements add to the complexity. The Madden-Julian Oscillation (MJO), a pulse of clouds and rain that travels eastward around the tropics every 30 to 60 days, can enhance or suppress rainfall depending on its position. The extent of snow cover over the Himalayas and Eurasia can also influence the temperature contrast that drives the monsoon. Furthermore, recent studies indicate the relationship between El Niño and the monsoon is not uniform across India and has been changing over time. The correlation has weakened over central India but has become stronger for north India in recent decades, meaning different parts of the country respond differently. This regional variation makes nationwide predictions even more challenging.
