Walker circulation
The Walker circulation (also Walker cell ) is a flow circuit of the air over the equatorial Pacific . The air sinks over the East Pacific (off South America ) and rises over the West Pacific (off Indonesia ). In between, it flows westward near the ground and backward eastward at the tropopause .
With an extension of over 120 degrees of longitude, the Walker cell is the largest cell in the equatorial circulation . This is less pronounced over the Indian Ocean and the Atlantic. In between, over the land masses, the air circulates in the opposite direction. The common drive mechanism: the Passat wind drives warm surface water off the east coast of the land masses and exposes cold deep water off the west coasts. Accordingly, low and high pressure areas are formed there . The low pressure areas are indicated by clouds in the figure.
The Walker Circulation is named after the English meteorologist Gilbert Walker (1868-1958) who discovered an anti-correlation between air pressure time series from the East and West Pacific in the 1920s . The long-wave fluctuations, some of them over years, were noticeable and required explanation. Known today as the cause: the sluggish displacement of water masses, see El Niño-Southern Oscillation (ENSO).