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contributor authorGrise, Kevin M.
contributor authorDavis, Sean M.
contributor authorStaten, Paul W.
contributor authorAdam, Ori
date accessioned2019-09-19T10:01:21Z
date available2019-09-19T10:01:21Z
date copyright6/7/2018 12:00:00 AM
date issued2018
identifier otherjcli-d-18-0060.1.pdf
identifier urihttp://yetl.yabesh.ir/yetl1/handle/yetl/4260679
description abstractAbstractIn recent decades, the subtropical edges of Earth?s Hadley circulation have shifted poleward. Some studies have concluded that this observed tropical expansion is occurring more rapidly than predicted by global climate models. However, recent modeling studies have shown that internal variability can account for a large fraction of the observed circulation trends, at least in an annual-mean, zonal-mean framework. This study extends these previous results by examining the seasonal and regional characteristics of the recent poleward expansion of the Hadley circulation using seven reanalysis datasets, sea level pressure observations, and surface wind observations. The circulation has expanded the most poleward during summer and fall in both hemispheres, with more zonally asymmetric circulation trends occurring in the Northern Hemisphere (NH). The seasonal and regional characteristics of these observed trends generally fall within the range of trends predicted by climate models for the late twentieth and early twenty-first centuries, and in most cases, the magnitude of the observed trends does not exceed the range of interdecadal trends in the models? control runs, which arise exclusively from internal variability. One exception occurs during NH fall when large observed poleward shifts in the atmospheric circulation over the North Atlantic sector exceed nearly all trends projected by models. While most recent NH circulation trends are consistent with a change in phase of the Pacific decadal oscillation (PDO), the observed circulation trends over the North Atlantic instead reflect 1) large natural variability unrelated to the PDO and/or 2) a climate forcing (or the circulation response to that forcing) that is not properly captured by models.
publisherAmerican Meteorological Society
titleRegional and Seasonal Characteristics of the Recent Expansion of the Tropics
typeJournal Paper
journal volume31
journal issue17
journal titleJournal of Climate
identifier doi10.1175/JCLI-D-18-0060.1
journal fristpage6839
journal lastpage6856
treeJournal of Climate:;2018:;volume 031:;issue 017
contenttypeFulltext


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