ENSO

El Nino

• Short-term climatic disruption
• Occurs at intervals between 2-7 years
• Typically lasts between 12-18 months
• Also known as ENSO warm event
• Arrival of warm surface water in the Eastern equatorial Pacific (off Peru and Equador)
• Often occurs at Christmas, giving name to event 'Christ Child'
• The current that brings cold water to the west coast of South America is called the Humbololts Current

Normal Air Circulation in the Central Pacific is called the Walker Loop

Process of a normal year of the El Nino Southern Oscillation

1. South East Trade Winds

• Part of global atmospheric circulation pattern.
• Not below -30 degrees and not above the equator.

2.Warm water builds up in Western Pacific

• Sea level is 50cm higher here.

3.Warm water heats the air causing convection currents and low pressure leading to high precipitation.

4.Tropical rainforest biome forms because of warm wet conditions

5.Cooler air sinks leading to dry conditions on the west coast of South America once the air has returned east.

Process of an El Nino year of the El Nino Southern Oscillation

1.South East trade winds drop

2.Warm water moves back towards the East

• Sea level on the Peruvian coast rises by 30cm

3.Air circulation reversed. Sinking air brings drought conditions to Western Pacific regions. Rising air causes convectional rainfall which can lead to floods in coastal areas of South America, which devastates the fishing industry.