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EL-NINO Circulations

What is El-Nino?

El-Nino is the term used to describe the occurrence of warm ocean surface waters off the shores of Ecuador and Peru. When the oceans warm, the regular upwelling of cool, nutrient-rich deep ocean water is greatly reduced.

El-Nio is a seasonal occurrence that occurs between Christmas and New Year's and lasts for a few weeks to a few months. It is conceivable for a very hot event to occur that lasts substantially longer than expected.

Normal Conditions in South Pacific

A typical year sees the formation of a surface low-pressure system between Northern Australia and Indonesia, and the formation of a high-pressure system off the coast of Peru.

As a result, the Pacific Ocean's trade winds blow strongly from east to west. The easterly trade winds carry warm surface water westward, generating convective storms (thunderstorms) across Indonesia and coastal Australia. Along Peru's coast, cold, nutrient-rich water rises to the surface to replace the warm water being dragged west.

El-Nino Conditions

Throughout much of the central Pacific and along the South American coast, air pressure drops during an El-Nio year. In the Western Pacific, a weak high-pressure system has displaced the normal pattern of low pressure. Due to changes in the pressure pattern, the trade winds are weakened.

The vertical circulation around the equator is created by a pattern of low and high pressures, with the ascending limb passing over areas of low pressure and the descending limb passing over areas of high pressure. This is referred to as Walker Circulation.

As a result, the walker cell is rendered ineffective. In some instances, the walker cell may be inverted. The equatorial counter-current (current that runs parallel to the doldrums) can now accumulate warm ocean water off the Peruvian and Ecuadorian shores.

The thermocline in the eastern Pacific Ocean descends as a result of the accumulation of warm water, preventing the upwelling of cold deep ocean water along Peru's coast. El Nino weather patterns bring drought to the Western Pacific, rain to the equatorial coasts of South America, and convective storms and hurricanes to the central Pacific.

What are the effects of El-Nino?

  • Marine life along Peru's and Ecuador's coasts suffers due to the warmer waters. The amount of fish captured off the South American coast is significantly less than in a regular year (Because there is no upwelling).

  • Australia, Indonesia, India, and Southern Africa experience extremely severe droughts.

  • California, Ecuador, and the Gulf of Mexico have all experienced significant rainfall.

  • In India, monsoon rainfall is reduced when the monsoon moves eastward from its normal position, as it happens during El Nio years. Positive and negative SOI (Southern Oscillation Index—pressure differential between Tahiti and Darwin) values determine whether India will get exceptional or insufficient rainfall.

The Southern Oscillation (SO) of the Indian Monsoon and the Southern Oscillation (SO) Index is a seesaw pattern of weather fluctuations between the Eastern and Western Pacific.

What is La Nina?

It is the polar opposite of El-polar Nino as part of the larger El-Nino Southern Oscillation Climatic Pattern. Additionally, it is referred to as 'small girl.' It's a situation that's virtually diametrically opposed to El Nino. The sea surface temperature of the western and central Pacific has fallen below normal.

The subtropical highlands of the Southern Pacific rise, bringing with them powerful trade winds. As a result of the trade winds blowing from east to west, the water is propelled, resulting in rapid upwelling of cold seas off the coast of Peru.

Effects of La-Nina

Tropical The west coast of South America is experiencing drier-than-normal conditions.

Drought is hurting the coastal regions of Peru and Chile.

The western equatorial Pacific's rainfall has risen (Indonesia, Malaysia and Northern Australia).

During the Northern Hemisphere winter season, South-East Africa and Northern Brazil experienced warmer temperatures than typical.

Throughout the summer months in India, the monsoon rainfall is typically greater than normal, particularly in North-West India. This trend, however, is not permanent, as both the Indian Ocean Dipole (IOD) and La Nina have an effect on the severity of the Indian monsoon.

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