Impacts of the Atlantic Warm Pool on Western Hemisphere Climate

Chunzai Wang

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The Atlantic warm pool (AWP) of water warmer than 28.50C is comprised of the Gulf of Mexico, the Caribbean Sea, and the western tropical North Atlantic. Unlike the Indo-Pacific warm pool, which straddles the equator, the AWP is entirely north of the equator. Sandwiched between North and South Americas and between the tropical North Pacific and Atlantic Oceans, the AWP is the second largest body of very warm water on Earth and hosts the second largest diabatic heating center of the tropics during the boreal summer. It has a large seasonal cycle and its interannual fluctuations of area and intensity are significant.

The AWP is a heating source of the summer Atlantic Hadley circulation and a source of moisture for North America. During August to October, large AWPs are associated with increased rainfall over the Caribbean, Mexico, the eastern subtropical Atlantic, and the southeast Pacific, and decreased rainfall in northwest US, Great Plains, and eastern South America. Large (small) AWPs correspond to a weakening (strengthening) of the northward surface winds from the warm pool region to the Great Plains that disfavors (favors) moisture transport for rainfall over the Great Plains. On the other hand, large (small) AWPs strengthen (weaken) the summer regional Hadley circulation that emanates from the warm pool region into the southeast Pacific, changing the subsidence over the southeast Pacific and thus the stratus cloud and drizzle there. The large AWP, associated with a decrease in sea level pressure and an increase in atmospheric convection and cloudiness, corresponds to a weak vertical wind shear between the upper and lower troposphere and thus increases Atlantic hurricane activity.

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22 December 2005
--Note: Special Thursday Seminar --
2 PM/ DSRC 1D 403
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