ENSO Occurs

Normally, surface winds in Pasific Ocean move from east to west. The trade winds blow from the normally high pressure are over the eastern Pacific (Near central and South merica) to normally low pressure area over the western Pacific (North of Australia). But sometimes cell circulation doesn’t seem to play by the rules. In three to eight year cycles, atmospheric circulation changes significantly from the pattern: hight pressure builds in the western Pacific and low pressure dominates the eastern Pacific. So, wind occross the tropical Pacific then reverse direction and blow from west to east and the trade winds weaken or reverse. This change in atmospheric pressure is called The Shoutern Oscillation.

The trade winds normally drag huge quantities of water westward along the ocean’s surface on each side of equator, but as the winds weaken, the equatoriel curretnts crawl to a stop. The eastward moving warm from water usually arrives near the south American. This current is called by El-Nino.

El-Nino and La-Nina phenomena are caupled, so these are combined from the acronym ENSO. The effects of this phenomena are felt not only in the Pacific , but all ocean areas at trade wind latitudes in both hemispheres can be affected.