Modeling Tidal Currents for MBP field site IRB

In order to predict tidal currents at the IRB field site we employed a least squares harmonic analysis routine based on analysis of in situ current measurements from the IRB database. Current measurements were made 1.0 meters above the bed. Observed current measurements were made available courtesy of Peter Howd at USF

A record of hourly mean current measurements from 2003, were chosen for the analysis. The tidal currents were rotated onto a projection along the dominant axis (Fig 1). The time series of mean currents were subjected to least squares harmonic analysis to determine the mean amplitude and phase of the first 9 tidal constants (Fig 2). Once determined from the analysis, the tidal constants were used to generate predicted currents for the entire period from 2001-2004. The predicted tidal currents can then be compared to actual observed currents (Fig 3). Hourly predicted currents for each year are available for download along with a readme file that describes the units, orientation, and time conventions used.

The values for the amplitude and phase of the tidal constants used in the model are summarized below in Table 1.

Table 1

The tidal predictions are available for download at http://www.vims.edu/physical/projects/CHSD/projects/MBP/forecasts/IRB_currents/

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

Figure 1. Scatterplot of 14 day hourly current record from IRB ADCP, sample height is 1.0m above the bed

Figure 2. 14 day comparison of observed (red), predicted (blue) and residual (green) mean currents from IRB

Figure 3. Three day comparison of measured (red), modeled (blue), and residual (green) currents for IRB.

Dr. John Boon of VIMS is thanked for use of his code for conducting the harmonic tidal analysis. An excellent matlab based GUI of this package is available at

http://www.vims.edu/physical/research/TCTutorial/TCT.htm

or by contacting directly to boon@vims.edu

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Last Updated: 4/01/2004

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