Why Even a Strong El Niño Does Not Guarantee a Poor Indian Monsoon, Pg II

Key Highlights:

• In 1997, a strong El Niño did not lead to a predicted monsoon deficit; India received nearly normal rainfall.
• The 2026 southwest monsoon concluded with rainfall 13% below the long-term average, marking the driest season for East and Northeast India since 1901.
• The Indian Ocean Dipole (IOD) entered a positive phase in 1997, which largely offset the negative impact of El Niño on the monsoon.
• In contrast, the IOD remained neutral in 2015, contributing to deficient rainfall despite a strong El Niño similar to 1997.
• The specific location of the warmest waters in the Pacific during an El Niño event also influences its effect on Indian monsoon rainfall.
• The India Meteorological Department (IMD) has refined its forecasting methods, including combining multiple global climate models since 2021.

El Nino Impact.jpg

Detailed Insights:

• The El Niño Southern Oscillation (ENSO) involves a weakening of Pacific trade winds, causing warm surface water to shift eastward towards South America.
• The descending warmer, drier air associated with El Niño over India typically suppresses rain cloud formation, leading to weaker monsoon rains.
• Historically, five out of seven moderate or strong El Niño years since 1950 have resulted in deficient Indian monsoon rainfall (at least 10% below average).
• The Indian Ocean Dipole (IOD) is a sea-saw phenomenon where a positive phase (warmer western Indian Ocean, cooler eastern) enhances monsoon rainfall over India.
• A 2024 study indicated that changes in the wind belt encircling Antarctica might have prevented the IOD from turning positive in 2015.
• Other atmospheric phenomena like the Madden-Julian Oscillation, high-pressure systems over the Iranian plateau, and moisture from the Arabian Sea can also influence monsoon performance.
• Accurate monsoon forecasts are critical for India, as approximately 40% of its farmland is rain-fed, directly impacting agricultural output and food prices.

Key Concepts Involved:

• El Niño Southern Oscillation (ENSO): A climate pattern characterized by periodic warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean.
• Indian Ocean Dipole (IOD): An irregular oscillation of sea surface temperatures in the Indian Ocean, with its positive phase generally beneficial for the Indian monsoon.
• Madden-Julian Oscillation (MJO): An eastward-moving disturbance of clouds, rainfall, winds, and pressure that propagates around the global tropics every 30-60 days.