What is an El Niño event and what effect does it have on global weather?

Under normal conditions the weather is like;

In a normal year the South East trade winds arising from the global circulation blow from east to west creating the following conditions:

• Warm surface waters of the pacific ocean are blown westwards pooling very warm water near Australasia
• The warm water heats the air in the western pacific, creating intense convection and thunderstorm activity
• In the eastern pacific, the removal of warm surface water allows cool, deeper water to rise
• Cool up welling water near Peru creates higher air pressures on the coast of Peru, helping to reinforce the trade wind circulation.  Up welling water is also rich in nutrients, helping to boost the fishing industry.

El Niño and La Niña conditions;

If the South East trade winds weaken, a chain of events takes place to create a new condition in the pacific:

• The warm water piled up in the western Pacific by the trade winds slides back eastwards across the ocean
• The arrival of this warm water at the coast of Peru (El Niño) results in convectional rainfall
• The low pressure resulting from this warm water cause winds to switch direction and blow from west to east, reinforcing the El Niño effect
• The lack of up welling water offshore Peru causes fish stocks to decline as nutrients are used up
• Air descends in the western Pacific to compensate for rising convectional air near Peru
• High pressures develops near Australasia, rainfall ceases and drought develops

From the information above it is shown that an El Niño can and does affect weather all around the world.  It causes floods and droughts and plays with the Earth’s atmosphere. An El Niño is associated with many global weather changes, mainly the rise in water temperature, which can lead to a rise in precipitation.

There have been 26 El Niños recorded to date, over the succeeding years, scientists studied the El Niños, and linked the warm water to increased rainfall in the Southeast United States, and to droughts in Indonesia, Australia, Ethiopia and Zimbabwe.