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Odblog

A weblog designed to share Geography resources with students and colleagues

Tuesday, May 26, 2009

El Nino and other things

Categories: Atmosphere, Geography General
I opened my mail last night and noticed in the spam box someone requesting access to the higher wiki. PBworks now require accounts for users or invites, so students can't log on and make anonymous changes anymore, which was one of the features I liked about the old wiki page. It meant that anyone could ask a question without everyone else knowing they were seeking assistance, and also meant that people were more likely to collaborate on an answer as their mistakes weren't public.

Anyway, the question related to El Nino and La Nina, which we covered (not in great detail) when looking at the atmosphere topic. Here's my attempt to explain it:

El Nino and La Nina are NOT surface winds, but are very much affected by the Trade Winds and, in particular, the varying strength of these. In normal conditions, the Trade Winds will push warm water westwards towards Australia and Indonesia. This allows for an upwelling of cold water from the deep ocean basins along the Pacific coast of South America. This brings dry conditions, but also incredibly nutrient rich waters which support fishing industries in countries such as Peru and Chile. The warm water travelling westwards has higher evaporation rates and brings rainfall to the western Pacific. During El Nino, the Trade Winds weaken. This means that the movement of warm water is slower and the effect of the upwelling of cold water is greatly hampered. In the Eastern Pacific, this can result in devastation for coastal industries, but also flooding, as the weather is wetter than normal, while in the Western Pacific, the lack of warm water results in less evaporation, less rainfall, drought and forest fires in places like Australia. However, the change is not limited to the Pacific, and El Nino can result in changes to global atmospheric conditions. La Nina usually comes after an El Nino event, and sees the cold water extending further across the Pacific out from the South American coastline as the Trade Winds strengthen. The science behind El Nino/ La Nina is not precise, and it is difficult to predict the strength or frequency of the events. Hope this helps. You could always listen to the Super Furry Animals take on it instead, Northern Lights...which, if nothing else will be one of the more bizarre videos you'll watch anytime soon!

Best of luck everyone. I'll hopefully be in early providing I remember to plug the alarm in tonight (bit of a rush this morning!), come up and see me if you have any last minute queries.

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