Article Type:
Research Article

Large-Scale Variability of the Main Thermocline Excited by Stochastic Wind Stress Forcing

Martina M. Junge Meteorologisches Institut Universität Hamburg, Hamburg, Germany

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J-S. von Storch Meteorologisches Institut Universität Hamburg, Hamburg, Germany

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J. M. Oberhuber Deutsches Klimarechenzentrum GmbH, Hamburg, Germany

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Print Publication:
01 Aug 2000
DOI:
https://doi.org/10.1175/1520-0442(2000)013<2833:LSVOTM>2.0.CO;2
Page(s):
2833–2840
Restricted access

Abstract

To investigate the role of stochastic forcing in generating decadal variability in the main thermocline circulation, an isopycnic numerical model is forced by the standard monthly climatological forcings plus daily wind stress anomalies. Two statistical models of daily wind stress anomalies are developed. The first one simulates both the temporal and spatial second moment statistics of the observations, whereby it produces realistic daily wind stress anomalies. The second model produces spatially uncorrelated wind stress anomalies that have the observed local variance at each grid point.

The results show that a basinwide mode, characterized by a dipole structure in the heat content of the North Pacific, can be excited stochastically. The structure of the mode does not represent an imprint of the atmospheric forcing but is selected by the ocean itself.

* Current affiliation: Department of Meteorology, University of Reading, Reading, United Kingdom.

Corresponding author address: Dr. Martina M. Junge, Department of Meteorology, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB, United Kingdom.

Abstract

To investigate the role of stochastic forcing in generating decadal variability in the main thermocline circulation, an isopycnic numerical model is forced by the standard monthly climatological forcings plus daily wind stress anomalies. Two statistical models of daily wind stress anomalies are developed. The first one simulates both the temporal and spatial second moment statistics of the observations, whereby it produces realistic daily wind stress anomalies. The second model produces spatially uncorrelated wind stress anomalies that have the observed local variance at each grid point.

The results show that a basinwide mode, characterized by a dipole structure in the heat content of the North Pacific, can be excited stochastically. The structure of the mode does not represent an imprint of the atmospheric forcing but is selected by the ocean itself.

* Current affiliation: Department of Meteorology, University of Reading, Reading, United Kingdom.

Corresponding author address: Dr. Martina M. Junge, Department of Meteorology, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB, United Kingdom.

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