El Niño events in India have paradoxically intensified extreme daily rainfall, according to a research published in the journal Science on September 18.
Typically, El Niño events in the equatorial Pacific are responsible for decreasing summer rainfall, however, in the context of India, it is causing intensified extreme daily precipitation amounts. Throughout India, the study—using observational data spanning 1901 to 2020—found that El Niño events counter intuitively, simultaneously intensify extreme daily rainfall.
The researchers analysed India Meteorological Department (IMD) daily rainfall records spanning 1901 to 2020 to understand the connection between rainfall in India and El Niño. “This is partly driven by increases in extreme daily values of convective buoyancy, provided that both the undilute instability of near-surface air and the dilution by mixing with drier air above are considered,” stated the study.
Led by Spencer A Hill from City College of New York, US, the study found a direct connection between Indian rainfall and El Niño. “You tend to get more days with extreme amounts of rainfall within India, not less, in El Niño summers,” Hill told Down To Earth.
The findings were unusual because it has been known for over a century that El Niños events typically promote drought by decreasing total rainfall during the monsoon season, Hill added.
El Niño & Indian Summer Monsoon
An El Niño condition means that the oceanic temperatures in the eastern equatorial Pacific Ocean become warmer than the average (0.5°C above the long-term average) and east winds blow weaker than normal, according to Carbon Impacts.
The amount of rainfall that India receives during summer monsoon period between June and September varies each year. This year-to-year variation is known as the interannual variability of monsoon and is dependent on many factors.
Carbon Impacts noted that about 30% of the yearly variability is attributed to other climatic factors such as the Indian Ocean Diapole (IOD), Atlantic sea surface (SST) variability, North Atlantic Oscillation (NAO), Pacific Decadal Oscillations (PDOs). In addition, more short-term and local factors such as dust clouds and agricultural use of water also play a significant role in shaping the pattern of rainfall in India.
