Publication Date:
2022-05-25
Description:
Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Physica D: Nonlinear Phenomena 237 (2008): 584-599, doi:10.1016/j.physd.2007.09.025.
Description:
A simple heuristic model of coupled decadal ocean–atmosphere modes in middle
latitudes is developed. Previous studies have treated atmospheric intrinsic variability
as a linear stochastic process modified by a deterministic coupling to the ocean.
The present paper takes an alternative view: based on observational, as well as
process modeling results, it represents this variability in terms of irregular transitions
between two anomalously persistent, high-latitude and low-latitude jet-stream
states. Atmospheric behavior is thus governed by an equation analogous to that describing
the trajectory of a particle in a double-well potential, subject to stochastic
forcing. Oceanic adjustment to a positional shift in the atmospheric jet involves
persistent circulation anomalies maintained by the action of baroclinic eddies; this
process is parameterized in the model as a delayed oceanic response. The associated
sea-surface temperature anomalies provide heat fluxes that affect atmospheric
circulation by modifying the shape of the double-well potential. If the latter coupling
is strong enough, the model’s spectrum exhibits a peak at a periodicity related
to the ocean’s eddy-driven adjustment time. A nearly analytical approximation of
the coupled model is used to study the sensitivity of this behavior to key model
parameters.
Description:
This research
was supported by National Science Foundation grant OCE-02-221066 (all coauthors)
and the Department of Energy grant DE-FG-03-01ER63260 (MG
and SK).
Keywords:
Coupled climate variability
;
Stochastic models
;
Double-well potential
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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