An unusual warming of surface ocean waters in the eastern tropical Pacific is the concept that is known as El Nino.
– It is a strip of warm ocean water that develops in the central and east central equatorial Pacific. This is one part of Southern Oscillation. Since the ocean warming and pressure reversals are almost always simultaneous, this phenomenon is termed as El Nino by the scientists.
– The exact reason behind the formation of El Nino is not yet fully understood and is believed that the 1993 Mississippi and 1995 California floods may have been caused by El Nino, as well as the evasion of hurricanes in the North Atlantic which spared states like Florida from serious damage.
– El Nino was initially recognized by fishermen in 1600s, off the coast of South America, with the occurrence of remarkably warm water in the Pacific Ocean. The name was given based on the time of year which was December, during which this even occurred.
– El Nino may include increased surface pressure over the Indian Ocean, Australia and Indonesia along with a fall in air pressure over eastern and central Pacific ocean and Tahiti. There is a rise in warm air near Peru, causing rain in the northern Peruvian deserts.
Effect on India:
– Since El Nino is a condition lasting for almost a year, the period coincides with the warming of sea surface temperatures affecting wind patterns and causing floods and droughts in different parts of the world.
– A study has revealed that El Nino and Indian monsoon are inversely related. It is believed that some of the most prominent droughts in India have been caused by El Nino.
– However, there also exist facts that El Nino did not necessarily trigger droughts, proven by a strong El Nino in 1997-98 did not lead to a drought whereas a moderate one in 2002 lead to one of the worst droughts.
– During the El Nino year in India, the rainfall is below normal, which has an effect on crop production.
– El Nino directly impacts India’s agricultural economy as it causes a lowering in the production of summer crops such as rice, sugarcane, cotton and oilseeds.
– The lasting impact is seen in the form of rising prices and overall lower growth in the domestic product. This has a greater impact since agriculture contributes to around 14% of the Indian economy.
La Nina is a phenomenon opposite to El Nino. This is caused due to less heating which leads to cold sea water off the western South America Coast, eventually making it a high-pressure zone.
– This causes the moist sea winds to be pushed towards the Indian Ocean, thus increasing the chance of normal or excessive rainfall in India.
– As a common belief, El Nino is not caused by global warming. It is a climate change occurring at intervals.
– Prediction of El Nino can be done with the help of two major systems- the hydrodynamic coupled ocean-atmospheric model, or statistical models.