During the last five years, barring 2023, the southwest monsoon has been bountiful with normal and above normal rainfall from June to September. The big question is whether this run will be upset by the development of El Niño conditions later this year—according to the latest update from the World Meteorological Organization (WMO)—which negatively impacts the monsoon. This factor refers to the warming of sea surface waters in the central and eastern tropical Pacific Ocean, which has been associated with deficient and below normal rainfall in the country. The cooling of such waters is referred to as the La Niña factor which results in a marked increase in rainfall. Temperatures are already beginning to climb in many parts of the country, presaging much hotter summer months according to the India Meteorological Department (IMD).
El Niño Threat
As if all of this weren’t grounds for concern, research published in Geophysical Research Letters highlighted that patterns of salt distribution in the Pacific Ocean can increase the intensity of El Niño by 20% and almost double the probability of an extreme event occurring. If El Niño conditions are indeed strong, this is bad news that can result in severe drought conditions in the country. Meteorological experts, however, urge caution on drawing inferences on the El Niño factor. Madhavan Nair Rajeevan, a former secretary in the ministry of earth sciences, has reportedly stated that there was no need for panic as a better idea will emerge by June; that such conditions are expected to develop in the second half of the monsoon season and are likely to be moderate according to current predictions.
Beyond El Niño
Although this highly complex, dynamic system arrives with unfailing regularity, there are other factors also responsible for its behaviour—like the Indian Ocean Dipole (IOD), Eurasian snow cover, and Madden-Julian Oscillation.
While positive IOD conditions are good for rainfall, negative conditions—due to cooler sea surface temperatures in the western Indian Ocean relative to the warmer sea surface temperatures in the eastern Indian Ocean—have the effect of suppressing monsoon bursts over the Indian subcontinent. Eurasian snow cover has an inverse relationship with the monsoon. The Madden-Julian Oscillation, an equatorial travelling pattern of anomalous rainfall, also impacts the monsoon. While El Niño conditions are associated with deficient and below normal rainfall, the relationship is actually far more complex. While El Niño conditions undeniably had an impact on deficient southwest monsoon rainfall during 2014 and 2015, for instance, its impact was less clear on other episodes of below normal rainfall in the country. During 2017, warm neutral conditions prevailed during the first half of the monsoon season while cooler conditions characterised the second half, which led the IMD in its end season report to infer the absence of El Niño’s influence.
Similarly, in 2018, the IMD stated that the direct impact of the evolving El Niño on the monsoon was limited. In 2023, while El Niño conditions correlated with below normal rainfall, positive IOD conditions in the monsoon’s second half offset this deficiency. Greater clarity on the El Niño factor will of course become available when the IMD makes its first long-term forecast for the monsoon by April. But as they say, to be forewarned is to be forearmed. Contingency plans must be put in place if El Niño conditions develop this year that can affect the monsoon as indicated by agencies like the WMO.