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contributor authorDiNezio, Pedro N.
contributor authorDeser, Clara
date accessioned2017-06-09T17:09:56Z
date available2017-06-09T17:09:56Z
date copyright2014/10/01
date issued2014
identifier issn0894-8755
identifier otherams-80411.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4223300
description abstractlarge fraction (35%?50%) of observed La Niña events last two years or longer, in contrast to the great majority of El Niño events, which last one year. Here, the authors explore the nonlinear processes responsible for the multiyear persistence of La Niña in the Community Climate System Model, version 4 (CCSM4), a coupled climate model that simulates the asymmetric duration of La Niña and El Niño events realistically. The authors develop a nonlinear delayed-oscillator (NDO) model of the El Niño?Southern Oscillation (ENSO) to explore the mechanisms governing the duration of La Niña. The NDO includes nonlinear and seasonally dependent feedbacks derived from the CCSM4 heat budget, which allow it to simulate key ENSO features in quantitative agreement with CCSM4.Sensitivity experiments with the NDO show that the nonlinearity in the delayed thermocline feedback is the sole process controlling the duration of La Niña events. The authors? results show that, as La Niña events become stronger, the delayed thermocline response does not increase proportionally. This nonlinearity arises from two processes: 1) the response of winds to sea surface temperature anomalies and 2) the ability of thermocline depth anomalies to influence temperatures at the base of the mixed layer. Thus, strong La Niña events require that the thermocline remains deeper for longer than 1 yr for sea surface temperatures to return to neutral. Ocean reanalysis data show evidence for this thermocline nonlinearity, suggesting that this process could be at work in nature.
publisherAmerican Meteorological Society
titleNonlinear Controls on the Persistence of La Niña
typeJournal Paper
journal volume27
journal issue19
journal titleJournal of Climate
identifier doi10.1175/JCLI-D-14-00033.1
journal fristpage7335
journal lastpage7355
treeJournal of Climate:;2014:;volume( 027 ):;issue: 019
contenttypeFulltext


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