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GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 23, 2133, doi:10.1029/2002GL015874, 2002

A simple coupled model of tropical Atlantic decadal climate variability

Yochanan Kushnir

Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, USA


Richard Seager

Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, USA


Jennifer Miller

Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, USA


John C. H. Chiang

Joint Institute for the Study of Atmosphere and Ocean, University of Washington, Seattle, Washington, USA
Department of Geography, University of California, Berkeley, California, USA


Abstract

A linear, zonally averaged model of the interaction between the tropical Atlantic (TA) atmosphere and ocean is presented. A balance between evaporation and meridional heat advection in the mixed layer determines the sea surface temperature tendency. The atmosphere is a fixed-depth, sub-cloud layer in which the specific humidity anomaly is determined by a steady-state balance between evaporation, meridional advection, and a parameterized humidity exchange with the free atmosphere. When the model is integrated, forced with observed surface wind anomalies from 1965 to the present, its simulation of the observed sea surface temperature (SST) is realistic and comparable to a simulation with a full ocean GCM. A statistical representation of surface winds and their relationship to the SST gradient across the equator is used to formulate and test a coupled model of their regional variability. Forced on both sides of the equator, in the trade-wind regions, with “white-noise” windspeed perturbations, the SST-wind relationship in the near-equatorial region feeds back positively on existing SST anomalies and gives rise to decadal variability.

Published 13 December 2002.

Index Terms: 0312 Atmospheric Composition and Structure: Air/sea constituent fluxes (3339, 4504); 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3374 Meteorology and Atmospheric Dynamics: Tropical meteorology; 4255 Oceanography: General: Numerical modeling.

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Citation: Kushnir, Y., R. Seager, J. Miller, and J. C. H. Chiang (2002), A simple coupled model of tropical Atlantic decadal climate variability, Geophys. Res. Lett., 29(23), 2133, doi:10.1029/2002GL015874.