Smita Mishra
Also known as Southern Oscillation, El Nino is technically an abnormal warming of surface ocean waters in the eastern tropical Pacific Ocean.
The Southern Oscillation is the see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific. Because the ocean warming and pressure reversals are, for the most part, simultaneous, scientists call this phenomenon the El Nino/Southern Oscillation or ENSO for short.
Origin of El Nino dates back to 1500 AD when the fishermen of South America noticed the unusually warm water currant that came to their shore every few years near Christmas time. They christened it El Nino which means "the Christ Child" in Spanish.
The formation of El Nino is still a mystery for the scientists and it is blamed for several unusual climatic changes across the globe. El Nino is said to be behind a number of floods and drought conditions the world over.
Is it of recent origin?
The existence of El Nino was known from past four hundred years but it is only since a decade that the attention of the scientists has shifted to this amazing jaunt of nature. The El Nino of 1997-1998 is believed to be stronger than ever before. It caused a lot of climatic turbulences the world over-and the culprit-El Nino became suddenly famous.
It was realized that the condition which results in hot water first coming to the coasts of Peru and Ecuador in South America is responsible for causing grave climatic mishaps the world over. The impact of El Nino is long lasting because the warm El Nino phase typically lasts for 8–10 months.
What happens actually?
During El Nino, the trade winds blow calmly in the central and western Pacific. This allows warm water to accumulate on the surface, which results in nutrient depletion, leading to the killing of plankton and fish and the starvation of many seabirds. The warm water on surface that extends to kilometers heats the air overhead, resulting in formation of moisture laden clouds. These are all El-Nino effects that are responsible for destructive disruptions of worldwide weather patterns.
Spelling disaster
A number of disasters have been blamed on the El-Nino effect including the 1983 Indonesian famine, bush fires in Australia arising from droughts, California rainstorms, and mass killing of fishes in Peru. In the same year it is said to have led to the death of some 2000 people worldwide and caused losses amounting to approximately 12 billion dollars.
But the 1997/98 El Nino was the most damaging. Americas were hit by floods, storms devastated China, drought affected Austria, and forest fires burnt parts of South-East Asia and Brazil. Indonesia experienced the worst drought in the last 50 years and in Mexico, the town of Guadalajara saw snow for the first time since 1881. In the Indian Ocean, it badly affected the movement of the monsoon winds.
La Nina
Also sometimes referred to as El Viejo, La Nina generally follows El Nino. La Nina which means’ little girl’ is the cooling of water in the Pacific Ocean.
It is characterized by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Nino, which is characterized by unusually warm ocean temperatures in the region. Typically, La Nina occurs roughly half as often as El Nino.
The impacts of La Nina on the global climate and ocean temperature tend to be opposite those of El Nino. In the US, winter temperatures are warmer than normal in the south-east and cooler than normal in the north-west during a La Nina year. Snow and rain is experienced on the west-coast and unusually cold weather in Alaska. During this period there are higher than normal number of hurricanes in the Atlantic.
El Nino and La Nina are the most powerful phenomenon on the earth and alter the climate across more than half the planet.
El Nino and Monsoons
In India El Nino has often played the weather spoil sport. Most of the severe droughts over India are associated with it but monsoons do not fail in every El Nino year.
In 1997, a predicted drought didn`t occur but in 2002 and 2004, unexpected and severe can increase the amount of rainfall during the monsoon.
This year too, the scanty and unevenly spread monsoons are being blamed on El Nino. But this has not yet been proved by the weather scientists.
Our economy which is agriculture based and heavily dependent on monsoons, swings on the mercy of this erratic weather condition, the genes of whose origin, the scientists are yet to decode.
