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Title: Surface currents and equatorial thermocline in a coupled upper ocean-atmosphere GCM

Abstract

The Oregon State University coupled upper ocean-atmosphere GCM is evaluated in terms of simulated winds, ocean currents and thermocline depth variations. Although the zonal wind velocities in the model are underestimated by a factor of about three and the zonal current velocities are underestimated by a factor of about five, the model qualitatively simulates the major features of the gyral scale currents, and the phases of the seasonal variation of the principal equatorial currents are in reasonable agreement with observations. The simulated tropical currents are dominated by Ekman transport and the eastern boundary currents do not penetrate far enough equatorward, while the western boundary currents do not penetrate far enough poleward. The subtropical trade wind belt and the mid-latitude westerlies are displaced equator ward of observations; hence, the mid-latitude eastward currents, principally the Kuroshio-North Pacific Drift and the Gulf Stream-North Atlantic Current are displaced equatorward. In spite of these shortcomings the surface current simulation of this two-layer upper ocean model is comparable with that of other ocean GCMs of coarse resolution. The coupled model successfully simulates the deepening of the thermocline westward across Pacific as a consequence of the prevailing Walker circulation. The region of most intense simulated surface forcingmore » is located in the western Pacific due to a southwestward displacement of the northeast trade winds; hence the equatorial Pacific is dominated by eastward propagation of thermocline depth variations. The excessively strong Ekman divergence and upwelling in the western Pacific cools the local warm pool, while incorrectly simulated westerlies in the eastern Pacific suppress upwelling and inhibit cooling from below. These features reduce the simulated trans-Pacific sea-surface temperature gradient, weakening the Walker circulation and the anomalies associated with the simulated Southern Oscillation.« less

Authors:
;  [1];  [2]
  1. Lawrence Livermore National Lab., CA (United States)
  2. State Univ. of New York, Stony Brook (United States)
Publication Date:
OSTI Identifier:
6533453
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Climate Dynamics; (United States)
Additional Journal Information:
Journal Volume: 7:3; Journal ID: ISSN 0930-7575
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ATMOSPHERIC CIRCULATION; GENERAL CIRCULATION MODELS; OCEANIC CIRCULATION; EQUATOR; GULF STREAM; SEAS; SEASONAL VARIATIONS; SIMULATION; SOUTHERN OSCILLATION; TEMPERATURE DEPENDENCE; WIND; CURRENTS; MATHEMATICAL MODELS; SURFACE WATERS; VARIATIONS; WATER CURRENTS; 540110*; 540310 - Environment, Aquatic- Basic Studies- (1990-)

Citation Formats

Sperber, K R, Gates, W L, and Hameed, S. Surface currents and equatorial thermocline in a coupled upper ocean-atmosphere GCM. United States: N. p., 1992. Web. doi:10.1007/BF00211154.
Sperber, K R, Gates, W L, & Hameed, S. Surface currents and equatorial thermocline in a coupled upper ocean-atmosphere GCM. United States. doi:10.1007/BF00211154.
Sperber, K R, Gates, W L, and Hameed, S. Wed . "Surface currents and equatorial thermocline in a coupled upper ocean-atmosphere GCM". United States. doi:10.1007/BF00211154.
@article{osti_6533453,
title = {Surface currents and equatorial thermocline in a coupled upper ocean-atmosphere GCM},
author = {Sperber, K R and Gates, W L and Hameed, S},
abstractNote = {The Oregon State University coupled upper ocean-atmosphere GCM is evaluated in terms of simulated winds, ocean currents and thermocline depth variations. Although the zonal wind velocities in the model are underestimated by a factor of about three and the zonal current velocities are underestimated by a factor of about five, the model qualitatively simulates the major features of the gyral scale currents, and the phases of the seasonal variation of the principal equatorial currents are in reasonable agreement with observations. The simulated tropical currents are dominated by Ekman transport and the eastern boundary currents do not penetrate far enough equatorward, while the western boundary currents do not penetrate far enough poleward. The subtropical trade wind belt and the mid-latitude westerlies are displaced equator ward of observations; hence, the mid-latitude eastward currents, principally the Kuroshio-North Pacific Drift and the Gulf Stream-North Atlantic Current are displaced equatorward. In spite of these shortcomings the surface current simulation of this two-layer upper ocean model is comparable with that of other ocean GCMs of coarse resolution. The coupled model successfully simulates the deepening of the thermocline westward across Pacific as a consequence of the prevailing Walker circulation. The region of most intense simulated surface forcing is located in the western Pacific due to a southwestward displacement of the northeast trade winds; hence the equatorial Pacific is dominated by eastward propagation of thermocline depth variations. The excessively strong Ekman divergence and upwelling in the western Pacific cools the local warm pool, while incorrectly simulated westerlies in the eastern Pacific suppress upwelling and inhibit cooling from below. These features reduce the simulated trans-Pacific sea-surface temperature gradient, weakening the Walker circulation and the anomalies associated with the simulated Southern Oscillation.},
doi = {10.1007/BF00211154},
journal = {Climate Dynamics; (United States)},
issn = {0930-7575},
number = ,
volume = 7:3,
place = {United States},
year = {1992},
month = {4}
}