Tópico: Cidades podem estar atraindo furacões

[SnowRaptor]

Cities may be attracting hurricanes


Hurricane Katrina, which struck in 2005

Powerful hurricanes can wreak havoc when they strike heavily-populated coastal areas. New research shows that the cities themselves might be partly responsible for attracting these storms, with the extra friction created by “rough” landscapes such as tall buildings significantly diverting the path of a storm.
A hurricane, or tropical cyclone, is a system of winds rotating inwards to an area of low pressure. Stretching hundreds of kilometres across, they feed on the heat given off by moist air as it rises and condenses. As such, they form over large expanses of warm water – normally tropical seas – and lose strength if they reach land.

In May the National Oceanic and Atmospheric Administration (NOAA) in the US said that this season the Atlantic would probably see more hurricanes than normal, giving a 70% probability of between 3 and 7 really big storms in 2010. Currently, the NOAA is able to provide a 24-hour forecast of the position of a hurricane’s centre with a margin of error of about 100 km but it becomes especially difficult to predict the path of hurricanes once they reach land.

Scientists know that wind speeds drop significantly due to the extra friction that a hurricane experiences once it makes "landfall", and they have also observed how the reduction in moisture inland causes a hurricane to peter out. Now Johnny Chan and Andie Au-Yeung of the City University of Hong Kong in China have extended these analyses to find out the effects of variations in roughness and moisture levels over land.

They did this by using the Weather Research and Forecasting model to simulate a hurricane approaching a north-south coastline from the east and then passing over rough land. Roughness could be generated by tall buildings, hilly terrain or forests; marshland or agricultural land, for example would be smoother.

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[Geotecton]

Quando fiz a especialização em Gestão Ambiental em 2.005 perguntei a um professor e palestrista se existiam estudos quantificando a influência das "ilhas de calor" e da "topografia induzida" (expressão criada por mim na época para designar o relevo artificial urbano) proporcionadas pelas cidades e principalmente pelas grandes conurbações. Ele respondeu que alguma coisa exisitia sobre as "ilhas de calor" mas não conhecia nada sobre a "topografia induzida".

O estudo publicado no Journal of Geophysical Research (Atmospheres) afirma que muitos mais estudos ainda são necessários, mas me parece claro que aquilo que eu chamei de "topografia induzida" há 5 anos tem uma relevância significativa.