Contrasting the tropical responses to zonally asymmetric extratropical and tropical thermal forcing

TitleContrasting the tropical responses to zonally asymmetric extratropical and tropical thermal forcing
Publication TypeJournal Article
Year of Publication2014
AuthorsKang S.M, Held I.M, Xie SP
JournalClimate Dynamics
Date Published2014/04
Type of ArticleArticle
ISBN Number0930-7575
Accession NumberWOS:000334068100020
KeywordsAMOC; circulation; climate-change; energy budget; enso; gcm; itcz; Meridional overturning circulation; ocean-atmosphere model; pacific; thermohaline; Zonal advection; Zonal homogenization

The mechanism is investigated by which extratropical thermal forcing with a finite zonal extent produces global impact. The goal is to understand the near-global response to a weakened Atlantic meridional overturning circulation suggested by paleoclimate data and modeling studies. An atmospheric model coupled to an aquaplanet slab mixed layer ocean, in which the unperturbed climate is zonally symmetric, is perturbed by prescribing cooling of the mixed layer in the Northern Hemisphere and heating of equal magnitude in the Southern Hemisphere, over some finite range of longitudes. In the case of heating/cooling confined to the extratropics, the zonally asymmetric forcing is homogenized by midlatitude westerlies and extratropical eddies before passing on to the tropics, inducing a zonally symmetric tropical response. In addition, the zonal mean responses vary little as the zonal extent of the forced region is changed, holding the zonal mean heating fixed, implying little impact of stationary eddies on the zonal mean. In contrast, when the heating/cooling is confined to the tropics, the zonally asymmetric forcing produces a highly localized response with slight westward extension, due to advection by mean easterly trade winds. Regardless of the forcing location, neither the spatial structure nor the zonal mean responses are strongly affected by wind-evaporation-sea surface temperature feedback.

Short TitleClim. Dyn.
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