El Nino (Geography)
El Nino (Geography)
Why In News:
A leading American climate agency has reported that the ongoing El Nino event in the Pacific Ocean is strengthening and could become the most powerful since 1950, raising concerns about its impact on global weather patterns, including the Indian monsoon.
Source: The Indian Express, Page 13, 11 July 2026 - 'El Nino strengthens, could develop into strongest since 1950, says US agency'
What is El Nino?
El Nino is the warm phase of the El Nino Southern Oscillation (ENSO), characterised by unusual warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean.
Its counterpart, La Nina, is the cool phase, while ENSO Neutral refers to periods without significant warming or cooling.
ENSO is linked to changes in the Walker Circulation, the east-west atmospheric circulation pattern over the tropical Pacific.
Mechanism
Under normal conditions, trade winds push warm surface water westward towards Asia and Australia, allowing cold water to upwell along the coast of South America.
During El Nino, these trade winds weaken or reverse, allowing warm water to spread eastward, altering rainfall and pressure patterns across the globe.
Impact on India
El Nino years are historically associated with a weaker or deficient Southwest Monsoon, since it suppresses the low-pressure systems that drive monsoon rainfall over India.
This link is not absolute: a positive Indian Ocean Dipole (IOD), the temperature difference between the western and eastern Indian Ocean, has offset El Nino's effect in years such as 1997 and 2023.
Monitoring Agencies
In India, the India Meteorological Department (IMD) monitors ENSO conditions and issues seasonal monsoon forecasts.
Internationally, agencies such as the US National Oceanic and Atmospheric Administration (NOAA) track sea surface temperature anomalies in the Nino 3.4 region to classify ENSO strength.
The Nino 3.4 region is the standard reference zone in the equatorial Pacific used to measure El Nino and La Nina strength.