La Niña(LN) and El Niño(EN) are simply terms to describe the weather phenomenon that involves changing surface ocean temperatures in the central and eastern equatorial Pacific throughout the year. Both are phased of the El Niño Southern Oscillation Climate Pattern.

A LN occurs when the central and eastern Pacific Ocean, which is tropical in nature, experiences colder than average surface ocean temperatures. It has the opposite impact from EN, which occurs with warmer surface ocean temperatures. Both events influence weather patterns, ocean conditions and marine life.

EN and LN events happen every two to seven years, on average, but they don’t happen on a regular schedule. Typically, El Niño happens more often than La Niña.

               This current La Niña started in September 2020. The World Meteorological Organization (WMO),  predicts the La Niña will continue over the next six months, making it the first time this century that La Niña has returned for three consecutive years. They’ve dubbed the event a “triple dip” La Niña.

Under normal conditions in the Pacific Ocean, trade winds blow east to west along the equator, pushing warm surface waters from South America towards Asia. To replace that warm water, cold water rises from the depths — a process known as upwelling.

During LN events, trade winds are even stronger than usual, pushing more warm water toward Asia. El Niño happens when the trade winds along the equator weaken, pushing warmer waters over the eastern Pacific.

                        LEARNING WITH TIMES/AT HOME/WITHOUT CLASSES

  EI NINO

The oceanic atmospheric phenomenon wherein waters in the equatorial Pacific warm up abnormally due to weakening of trade winds is termed as El Nino. El Nino, means ‘little boy’ in Spanish. It is a weather system which re-emerges after a gap of about two to five years in the Pacific Ocean and its effects last for about 12 months on an average.

EN leads to warming of sea surface temperatures, which in turn affects wind patterns and triggers both floods and droughts in different parts of the world.

El NINO AND INDIAN MONSOON

This phenomenon affects rainfall in India during the Monsoon months. Trade winds normally blow westward from South America towards Asia during Indian monsoon months. Warming of the Pacific results in weakening of these winds. Moisture and the heat content thereby, gets limited and results in reduction and uneven distribution of rainfall across the Indian sub-continent.

LA NINA

means The Little Girl in Spanish. La Nina is also sometimes called “a cold event.”La Nina episodes represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. Global climate La Nina impacts tend to be opposite those of El Nino impacts.

              During normal conditions in the Pacific Ocean, trade winds take warm water from South America towards Asia. To replace that warm water, cold water rises from the depths, and the is called upwelling.

                  During La Nina, trade winds are even stronger than usual, pushing more warm water toward Asia. This leads to an increase in upwelling off the west coast of the Americas, which brings cold, nutrient-rich water to the surface.

EN and LN are opposite phases of what is known as the El Nino-Southern Oscillation (ENSO) cycle.