2. The periodic extension along the Peruvian coast of warm and saline equatorial current is called El Nino effect.
3. This current replaces the cold Peru or Humboldt Current and sea surface temperatures may increase by 10 degree centigrade.
4. It appears every fourth or seventh year.
5. This has widespread effect on the world’s climate when the cold Peru or Humboldt Current flows off the Peruvian coast there is always high pressure zone. It is centered around it in south Pacific.
6. At the same time there is always a low pressure region centered around Indonesia and South East Asia.
7. The appearance of warm ocean current off the Peruvian coast means that there will be low pressure in the South Pacific Ocean and a simultaneously high, pressure zone centered around Indonesia South East Asia.
8. Applying the simple principle that wind always blows from high pressure to low pressure, it can be shown that when there is normally cold flowing (the Peru or Humboldt Current) there is high pressure zone resulting in anti-cyclonic circulation. Thus the low pressure around Indonesia and South east Asia invites wind from this direction and the long passage of this wind over water makes it rain-ladder Subsequently we have rainfall in these regions.
9. On the contrary, the low pressure associated with the warming of the ocean curer and consequent high pressure over Indonesia and South East Asia region inhibits an formation of cyclones and depressions over Indonesia or Bay of Bengal. Not only El Nino effect over this region but it has disastrous consequences elsewhere, for example as the water warms up, it brings rainfall in the otherwise dry region of Peru.
The heavy rains in the otherwise desert regions of Peru kills many fishes as they are dependent on the plankton in the cold water. So much hydrogen sulphide can be released from rotting fish it can blacken paint. Floods occur in North America and drought in Australia and parts of Africa.
10. Then southern oscillation is the atmospheric component of El Nino. This component is an oscillation in the surface air pressure between the tropical eastern and the western Pacific Ocean waters. EL Niono and Southern oscillation as together known as ENSO.
11. La Nina is the cooling of water in Pacific Ocean. The name La-Nina originates from Spanish meaning ‘the girl.’
Effect of EL-Nino over India:
1. Whenever, El Nino appears there is bound to be arid condition in India.
2. In a total of 27 El Nino years since 1875 India experienced at least 10 percent less than normal rainfall 11 times.
3. On 15 other occasions when the Peruvian coast had experienced the appearance of El Nino, rainfall has been normal in India.
4. The interesting thing is that it never rained 10 percent of what is normal for India even once during an El Nino year.
5. In 1979, the monsoon experiment (Monex), the largest of its kind involving nations, saw the discovery of the dramatic bursts of energy over Indian west coast just before rains. But eight years later they are still to find a satisfactory explanation. They now believe that Tibet holds the clue for many of the unexplained phenomena.