Upwelling Circulation on the Oregon Continental Shelf. Part II: Simulations and Comparisons with Observations

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  • 1 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
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Abstract

Sixty-day simulations of flow on the Oregon continental shelf are performed using the Blumberg and Mellor sigma coordinate, primitive equation model. The model is two-dimensional (an across-shelf section) with high spatial resolution and realistic shelf topography. Forcing consists of surface heat flux, either hourly or low-pass filtered wind stress, and in one case, a constant alongshore pressure gradient. Model results are compared with current and hydrographic measurements from the CUE-2 program. The horizontal scale of the alongshore coastal jet is significantly influenced by the structure of the initial density and velocity fields. The model successfully reproduces the vertical shear in the alongshore velocity field v, but the model's mean v field is too strongly southward, and the variance in both the vvu and v fields is underpredicted. Inclusion of the alongshore pressure gradient, while improving prediction of the mean alongshore velocities, does not improve the model-data correlation. The time-mean model density agrees with observations at middepths over the shelf, but shows larger values than observed near the surface. The results demonstrate the importance of including a surface heat flux and of specifying realistic initial density and alongshore velocity fields.

Abstract

Sixty-day simulations of flow on the Oregon continental shelf are performed using the Blumberg and Mellor sigma coordinate, primitive equation model. The model is two-dimensional (an across-shelf section) with high spatial resolution and realistic shelf topography. Forcing consists of surface heat flux, either hourly or low-pass filtered wind stress, and in one case, a constant alongshore pressure gradient. Model results are compared with current and hydrographic measurements from the CUE-2 program. The horizontal scale of the alongshore coastal jet is significantly influenced by the structure of the initial density and velocity fields. The model successfully reproduces the vertical shear in the alongshore velocity field v, but the model's mean v field is too strongly southward, and the variance in both the vvu and v fields is underpredicted. Inclusion of the alongshore pressure gradient, while improving prediction of the mean alongshore velocities, does not improve the model-data correlation. The time-mean model density agrees with observations at middepths over the shelf, but shows larger values than observed near the surface. The results demonstrate the importance of including a surface heat flux and of specifying realistic initial density and alongshore velocity fields.

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