Journal of Geophysical Research: Atmospheres

Cover image for Vol. 121 Issue 1

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ISI Journal Citation Reports © Ranking: 2014: 19/175 (Geosciences Multidisciplinary)

Online ISSN: 2169-8996

Associated Title(s): Journal of Geophysical Research

Tropical atmospheric circulation and precipitation changing

As Earth's climate has warmed over the past several decades, atmospheric and hydrological cycle changes are being observed globally and regionally. For instance, Zhou et al. (2011) analyzed trends in the hydrological cycle in the tropics over the past 20-30 years using precipitation, cloud, and radiation data. In particular, they looked at Hadley and Walker cell atmospheric circulation patterns. Hadley circulation is a major circulation pattern in the tropical atmosphere in which air masses, warmed by the Sun, rise near the equator, then travel poleward, sink back toward Earth's surface in the subtropics, and return to the equator. Similarly, in the Walker circulation, air rises over the warmer parts of the oceans near the equator, travels zonally toward the colder parts, then sinks back to the surface. There are indications that both of these circulation patterns are changing with global warming and could be altering precipitation and cloud radiation distributions in the tropical regions. The researchers found that tropical precipitation has increased in regions where air rises in Walker and Hadley circulation and has decreased in regions where air masses sink. They also found a poleward shift of subtropical dry zones and a broadening of the Hadley circulation. In general, they found that wet and dry extremes are intensifying; wetter areas are becoming wetter and dry areas have become drier. These results support other studies that have found that the strengthening tropical hydrological cycle and expanding Hadley cell trends are likely related to global warming.

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