Walker circulation

The Walker circulation or equatorial circulation is a parallel to the equator air circulation. In it the Coriolis force does not work, because it is located directly above the equator. It is caused by the warm ocean currents off the East Coast and the cold ocean currents off the west coasts of the land masses. She is responsible for the weather phenomena El Niño and La Niña.

This zonal air circulation, which is superimposed on the meridional circulation of air of the Hadley cells is caused by the presence of the Southeast Asian and Australian land masses. By the trade winds, the warm equatorial sea water is transported to the west and dammed up in front of the East Coast. Consequently, in the eastern Pacific off the coast of South America, cold deep water to rise ( upwelling ) or cold water shall flow from the Humboldt Current from the Antarctic. This causes air to circulate: While extending astonished warm water ( low pressure area, rainfall ) leads the Western Pacific to a rise of the air masses, the cold water makes in the eastern Pacific for a lowering of the air masses ( high pressure area, drought, and consequently there on the coast deserts as the Atacama ). About the Pacific therefore forms a circulation of air between the rising in the west and in the east sinking air - this is the Walker circulation. This circulation can only broad circle parallel ( zonal ) take place, since then the Coriolis force has no effect. The flows are there not deflected north or south. About the neighboring continents also form circulations, which are opposed to the Walker circulation, which means the air sinks on the west coast and rises on the east coast.

The Walker circulation is named after the English meteorologist Sir Gilbert Walker (1868-1958), the so-called Southern Oscillation, a correlation between high air pressure over the eastern Pacific and low pressure over the western Pacific discovered in the 20s of the twentieth century.

With climate phenomena such as El Niño or its counterpart in the Indian Ocean Walker cell is attenuated over the affected ocean or returns by as much as. From this reversal to great weather anomalies arise in the affected areas, such as droughts ( in the western Pacific ) or floods ( in the eastern Pacific ).