India Meteorological Department (IMD) said that El Nino Southern Oscillation (ENSO) neutral conditions would emerge in June and during July – September, ENSO would transition into La Nina.
Key Points
South peninsular and central India is expected to receive ‘above’ normal rainfall, northwest India would receive normal rainfall whereas east and northeast India is expected to receive below average rainfall during the June – September period.
About El Niño-Southern Oscillation (ENSO)
It is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean.
In periods ranging from about three to seven years, the surface waters across a large swath of the tropical Pacific Ocean warm or cool by anywhere from 1°C to 3°C, compared to normal.
This oscillating warming and cooling pattern, referred to as the ENSO cycle, directly affects rainfall distribution in the tropics and can have a strong influence on weather across different parts of the world.
ENSO is one of the most important climate phenomena on Earth due to its ability to change the global atmospheric circulation, which in turn, influences temperature and precipitation across the globe.
ENSO Phases and Impacts
El Niño: A warming of the ocean surface, or above-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.
Over Indonesia, rainfall tends to become reduced while rainfall increases over the central and eastern tropical Pacific Ocean.
The low-level surface winds, which normally blow from east to west along the equator (“easterly winds”), instead weaken or, in some cases, start blowing in the other direction (from west to east or “westerly winds”).
In general, the warmer the ocean temperature anomalies, the stronger the El Niño (and vice-versa).
La Niña: A cooling of the ocean surface, or below-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.
Over Indonesia, rainfall tends to increase while rainfall decreases over the central and eastern tropical Pacific Ocean.
The normal easterly winds along the equator become even stronger. In general, the cooler the ocean temperature anomalies, the stronger the La Niña (and vice-versa).
Neutral: Neither El Niño or La Niña. Often tropical Pacific SSTs are generally close to average.
However, there are some instances when the ocean can look like it is in an El Niño or La Niña state, but the atmosphere is not playing along (or vice versa).
Repercussions for India
The El Nino Southern Oscillation (ENSO) has had a greater impact on northern parts of India, a lesser impact on the central parts, and a relatively constant impact on the southern parts of the country in recent decades.
The warming phase known as the El Nino is generally known to suppress monsoon rainfall while the cooling phase known as the La Nina generally enhances monsoon rainfall.
Even though there are multiple other factors, like the monsoon low-pressure systems and depression, which affect the monsoon rainfall, La Nina is one of the major factors.
In a La Nina year, one could expect above-normal rainfall.
