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Climate Change - Macro Scale. What is the Walker Cell?

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Climate Change - Macro Scale What is the Walker Cell? This is the normal atmospheric conditions in the Pacific Ocean. The great NE and SE trade wind belts blow equatorward and westward across the width of the Pacific towards the warm water of the west. A convectional uplift occurs as the water heats up. Pressure rises over the eastern Pacific Ocean, off the coast of South America, and falls over the western Pacific Ocean, toward Indonesia and the Philippines. The descending air in the east gives the clear, dry conditions that create the Atacama Desert in Peru, whilst the warm, moist air ascending in the west gives heavy convectional rainfall. What are the atmospheric conditions in an El Nino year? During an El Nino year the normal conditions are reversed in the equatorial Pacific region, in pressure, precipitation and often in winds and ocean currents. Pressure rises over the western Pacific and falls over the eastern Pacific causing the region of rising air to move east with the associated convectional uplift. ...read more.


What changes in an El Nino Year? The whole system relaxes. What effect does an El Nino event have on the global climatic pattern? El Nino has a major effect on places far beyond the Pacific margins as well as on those bordering the ocean itself in its low latitudes. This is because the upper air disturbances distort the path of the jet streams, which can lead to teleconnections all around the world. Between 1997 and 1998 the largest El Nino event occurred. * Severe droughts were experienced in the Sahel and southern Africa as well as across the Indian subcontinent * There were extremely cold winters in central North America * Stormy conditions with floods in California * Exceptional wet, milt and windy winters were experienced in Britain and north-west Europe * In Peru for 12 days in early March, Peru received the equivalent of six months of normal rain. Over several months, flash flooding caused 292 deaths, injured more than 16000 people, left 400 missing, destroyed 13200 houses, wrecked 250000km of roads, swept away bridges, damaged crops, and schools, and disrupted the lives of up to half a million Peruvian. ...read more.


What global consequences are experienced when La Nina occurs? Globally La Ni�a in very general terms will mean that those parts of the world who normally experience dry weather will be drier and those with wet weather will be wetter. The Atlantic and Pacific hurricane activity will increase with La Ni�a and the effects of severe droughts are now being considered for those parts of the world who are already suffering. Broadly speaking, the La Ni�a event could give drier conditions in Central East Africa, SW USA, Northern Mexico, South America etc. Wetter conditions could be experienced in North/North East Australia, South Africa (which may cause further floodings similar to that in Mozambique and other countries in the region), Southern Asia (during the monsoon) and the northern half of South America, Central America and the Hawaiian Islands. Whilst historically these are the effects of a La Ni�a event, as we have seen with El Ni�o, nothing is certain and the global impact is still to be fully understood. ...read more.

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