El Nino likely increasing rainfall in India

El Niño and La Niña are climate patterns in the Pacific Ocean that can affect weather worldwide, as described on the US National Oceanic and atmospheric Administration (NOAA) website. Known to suppress monsoons, El Nino could however be contributing to increasing rainfall in India’s wetter regions, according to a study published in the Science journal.

Titled ‘More extreme Indian monsoon rainfall in El Niño summers’, the study finds that although the well-documented effect of El Niño events is to decrease summer rainfall, it also paradoxically intensifies extreme daily precipitation amounts, thereby resulting in hazardous conditions across the region.

As the Abstract of the study states, extreme rainfall during the Indian summer monsoon can be destructive and deadly to the world’s third-largest economy and most populous country. Although El Niño events in the equatorial Pacific are known to suppress total summer rainfall throughout India, the study shows, using observational data spanning 1901 to 2020 that, counterintuitively, they simultaneously intensify extreme daily rainfall. El Niño could plausibly drive similar changes in other tropical regions.

Highlighting this study, a Press Trust of India (PTI) report explains that El Nino is the warm phase of the larger ‘El Nino-Southern Oscillation (ENSO)’ cycle, during which warmer waters of the Pacific Ocean trigger unusual patterns of rising and sinking air, thereby suppressing seasonal rainfall across the Indian subcontinent on a large-scale. ENSO is known to alternate between El Nino, its cool counterpart ‘La Nina’ and a neutral phase – duration of one cycle can be between two and seven years. The study highlights the complex nature of El Nino’s impact – India’s drier areas experience fewer showers, while wet regions face more severe storms. It has also mentioned the significant implications for understanding climate variability in tropical zones.

An India Today analysis of the study says that researchers note that this change may indicate shifting mechanisms in the interaction between oceanic and atmospheric conditions and India’s monsoon system. The study’s findings extend beyond India, suggesting that the processes driving this intensification could play an important role in extreme rainfall variability due to climate change in other tropical locations. Typically known for weakening India’s monsoon and causing drought, El Nino may paradoxically increase the chance of extreme daily rainfall in the country’s wetter regions. Analysis of rainfall patterns over more than a century shows a sharp rise in the likelihood of intense downpours, even as moderate and light rains decrease during El Nino years. This suppression has stark effects. In India’s typically drier regions, El Nino often results in fewer rainy days and weaker showers, intensifying dryness. Conversely, in wetter areas, storms that do occur tend to be much more intense. Analysis of Indian rainfall records from 1901 to 2020 revealed that while light and moderate rains decline during El Nino, the probability of very heavy downpours climbs steeply in wetter regions. In some cases, extreme rainfall events become more than 50% likelier, leading to hazardous conditions. Unlike El Nino’s declining influence on India’s average summer rainfall in recent decades, its impact on extreme rainfall remains comparatively steady, though with some regional shifts. According to the authors, this intensification is linked to changes in atmospheric buoyancy and low-pressure system tracks.

The NOAA website explains El Niño can affect weather patterns significantly. El Niño means Little Boy in Spanish. South American fishermen first noticed periods of unusually warm water in the Pacific Ocean in the 1600s. The full name they used was El Niño de Navidad because El Niño typically peaks around December. The warmer waters cause the Pacific jet stream to move south of its neutral position. With this shift, areas in the northern US and Canada are dryer and warmer than usual. But in the US Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding. El Niño and La Niña can both have global impacts on weather, wildfires, ecosystems, and economies. They occur every two to seven years, on average, but not on a regular schedule. Generally, El Niño occurs more frequently than La Niña. During El Niño, trade winds weaken. Warm water is pushed back east, toward the west coast of the Americas.