Modeling Combined Tidal and Wind Driven Currents for MBP field site MVCO

In order to predict the combined tide and wind drive currents at the MVCO field site we have added a simple linear least squares model of wind driven currents to our tidal harmonic analysis routine based on analysis of in situ current measurements from the MVCO database. All current measurements were made 3.7 meters above the bed.

The entire record of hourly mean current measurements from 2002 were chosen for the analysis. From this record we next subtracted the predicted tidal component and regressed the remaining residual currents against the WW3 model hindcast values such that

X=[sqrt(U^2+V^2)]*U where U and V are the along and across-shelf waves.

The linear fit has a form Y=mX+b with the following values

Y=7.626e-4 X -.0197 (1)

The r for this model fit is 0.6258

Equation 1 can then be used to solve for the value of the residual current based on the model estimates of U and W winds

Next the modeled wind derived currents are added to the tidal currents to produce a total current vector for each model time step and compared to the observed data record (Figures 1 and 2).

The r value for the combined tide and wind model is r=0.9246.

Figure 1. Cross plot of total observed mean currents (X) to combined wind and tide model (Y)

Figure 2. Comparison of reconstructed current time series (red) to observed time series (blue).

for questions or comments contact Carl Friedrichs cfried@vims.edu or Art Trembanis art@vims.edu

Last Updated: 9/04/2003

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