Walker circulation

Walker circulation

The Walker circulation (or Walker cell) is an idealized air flow which forms, on average, zonal atmospheric circulation of air at the equator and its proximity. It is caused by differences in heat distribution between ocean and land. It was discovered by Gilbert Walker. Since then several meridional cells have been characterized in the tropical atmosphere.

Oceanic effects

The Walker cell is indirectly related to upwelling off the coasts of Peru and Ecuador. This brings nutrient-rich cold water to the surface, increasing fishing stocks.

El Niño

The Walker circulation is caused by the pressure gradient force that results from a high pressure system over the eastern Pacific ocean, and a low pressure system over Indonesia. When the Walker circulation weakens or reverses, an El Niño results, causing the ocean surface to be warmer than average, as upwelling of cold water occurs less or not at all. An especially strong Walker circulation causes a La Niña, resulting in cooler ocean temperatures due to increased upwelling.

A scientific study published in May 2006 in the journal Nature indicates that the Walker circulation has been slowing since the mid-19th Century. The authors argue that global warming is a likely causative factor in the weakening of the wind pattern. [http://www.gfdl.noaa.gov/research/climate/highlights/index.html#walker]

References

* Climate research summary - [http://www.gfdl.noaa.gov/research/climate/highlights/index.html#walker Walker Circulation: a tropical atmospheric circulation slow-down] Text and graphics from NOAA / Geophysical Fluid Dynamics Laboratory
* [http://www.eurekalert.org/pub_releases/2006-05/ncfa-sit050106.php Slowdown in tropical Pacific flow pinned on climate change ] - press release from University Corporation for Atmospheric Research.
* [http://www.nature.com/nature/journal/v441/n7089/abs/nature04744.html Weakening of tropical Pacific atmospheric circulation due to anthropogenic forcing ] 4 May 2006 in Nature (journal).
* [http://www.breitbart.com/news/2006/05/03/D8HCH8VO2.html Associated Press news story, 3 May 2006: "Global Warming Cited in Wind Shift"]

ee also

*Atmospheric circulation
*Earth's atmosphere


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