"While El Niño summers suppress total rainfall across India, they also increase the intensity of extreme daily rainfall, especially in central India and along the Western Ghats. Wet regions (Central Monsoon Zone, Western Ghats) see fewer rainy days but more powerful downpours, whereas dry regions (southeast and northwest India) see rainfall suppressed at all intensities. Stronger convective buoyancy (a mix of unstable near-surface air and moisture above) helps fuel these rainfall extremes during El Niño events. Seasonal forecasts could help anticipate likelihood of extreme rainfall events, but current forecast skill remains limited for practical use."
"A new study in the journal Science, led by scientists at the City College of New York (CCNY) and Columbia University, challenges long-held beliefs about how El Niño events influence rainfall during the Indian summer monsoon. The findings show that while El Niño often brings drought conditions to India overall, it also increases the likelihood of devastating downpours in some of the country's most heavily populated regions. "Our key finding is that you tend to get more days with extreme amounts of rainfall within India, not less, during El Niño summers," says lead author Spencer Hill, a professor at CCNY and an affiliate at the Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. "This result was unexpected, because we've known for over a century that El Niño events do precisely the opposite for total rainfall summed over the rainy season, June through September.""
El Niño summers suppress total seasonal rainfall across India while increasing the intensity and frequency of extreme daily rainfall events in central India and along the Western Ghats. Regions that are typically wet during the monsoon experience fewer rainy days but larger, more powerful downpours, while typically dry regions in the southeast and northwest see reductions in rainfall across all intensities. Enhanced convective buoyancy—unstable near-surface air combined with elevated moisture—helps fuel these extremes during El Niño. More than a century of observations combined with high-resolution datasets and atmospheric diagnostics reveal robust differences in extreme-event behavior. Seasonal forecasting offers potential to anticipate extremes, but forecast skill remains limited for operational use.
Read at State of the Planet
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