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

Journal Article · Wed Apr 01 04:00:00 EST 1992 · Climate Dynamics; (United States)

DOI:https://doi.org/10.1007/BF00211154· OSTI ID:6533453

Sperber, K R; Gates, W L ^[1]; Hameed, S ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. State Univ. of New York, Stony Brook (United States)

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.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6533453
• Journal Information: Climate Dynamics; (United States), Journal Name: Climate Dynamics; (United States) Vol. 7:3; ISSN 0930-7575; ISSN CLDYEM
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
540310 -- Environment
Aquatic-- Basic Studies-- (1990-)
ATMOSPHERIC CIRCULATION
CURRENTS
EQUATOR
GENERAL CIRCULATION MODELS
GULF STREAM
MATHEMATICAL MODELS
OCEANIC CIRCULATION
SEAS
SEASONAL VARIATIONS
SIMULATION
SOUTHERN OSCILLATION
SURFACE WATERS
TEMPERATURE DEPENDENCE
VARIATIONS
WATER CURRENTS
WIND