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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, C10S08, doi:10.1029/2004JC002493, 2005

Assimilation of moored velocity data in a model of coastal wind-driven circulation off Oregon: Multivariate capabilities

Alexander L. Kurapov

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


J. S. Allen

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


G. D. Egbert

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


R. N. Miller

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


P. M. Kosro

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


M. D. Levine

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


T. Boyd

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


J. A. Barth

College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA


Abstract

Horizontal current measurements from an array of moored acoustic Doppler profilers are assimilated sequentially into a model of coastal wind-driven circulation off Oregon during the upwelling season of May–August 2001. Model results are compared against independent moored and ship survey data to document a positive effect of velocity data assimilation (DA) on other oceanic variables of interest such as the sea surface height (SSH), temperature, potential density, surface salinity, and near-bottom turbulence parameters. Significant improvement is achieved for the nearshore SSH even when data are assimilated from only two moorings at an alongshore distance of 50 km from the SSH verification site. At 45°N, in an area of simple shelf bathymetry with relatively small alongshore variations, the model (even without DA) provides a good description of the isopycnal structure on a cross-shore section. At 44.2°N, over complicated bathymetry, velocity DA may improve the slope of isopycnals but at the same time not necessarily the density values themselves. Data assimilation based on a time-invariant representation of the forecast error covariance may inhibit spatial variability on horizontal scales smaller than the assumed forecast error decorrelation scale. An experiment involving assimilation of both velocity and moored salinity measurements demonstrates that moored velocity DA improves transport of buoyant surface water. The level of improvement in the near-bottom turbulent dissipation and bottom stress found with the DA model indicates that it is suitable for future studies of spatial and temporal variability in the bottom boundary layer off Oregon.

Received 17 May 2004; accepted 25 January 2005; published 29 September 2005.

Keywords: shelf circulation; modeling; data assimilation.

Index Terms: 4217 Oceanography: General: Coastal processes; 4219 Oceanography: General: Continental shelf and slope processes (3002); 4255 Oceanography: General: Numerical modeling (0545, 0560); 4260 Oceanography: General: Ocean data assimilation and reanalysis (3225).

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Citation: Kurapov, A. L., J. S. Allen, G. D. Egbert, R. N. Miller, P. M. Kosro, M. D. Levine, T. Boyd, and J. A. Barth (2005), Assimilation of moored velocity data in a model of coastal wind-driven circulation off Oregon: Multivariate capabilities, J. Geophys. Res., 110, C10S08, doi:10.1029/2004JC002493.