The IEEE Seventh Working Conference on Current Measurement Technology

Current and Wave Monitoring and Emerging Technologies

March 13-15 | Bahia Hotel | San Diego, CA, USA

  
     

A Comparison of Near-Surface Current Measurements by ADCP and HF-Radar on the West Florida Shelf

F.J. Kelly

Status: Accepted

Texas A&M University, Conrad Blucher Inst.
6300 Ocean drive
Corpus Christi , TX USA
78412

Phone: 361-825-5520
Email: fkelly@cbi.tamucc.edu

Co-Authors:
J.S. Bonner, J.C. Perez, D. Trujillo
Conrad Blucher Institute for Surveying and Science, Texas A&M University-Corpus Christi
R.H. Weisberg, R. He, and M.E. Luther
College of Marine Science, University of South Florida

We have examined the surface currents measured during a 12-day deployment of a pair of CODAR Ocean Sensors 25-MHz SeaSondeTM HF-Radars with those measured by the top bins (2 to 3 m below the surface) of an array of six acoustic Doppler Current profilers on the West Florida Shelf (WSF). The radar footprint had a maximum range of 60 km offshore, and it included mooring locations between the 10 m to 30 m isobaths. During the first 7 days strong NW (up to 12 m/s) and weaker NE winds prevailed. A 3-day transition of weak and variable winds was followed by persistent SE and S winds of ~5 m/s.

We first used principal component analysis, linear regression, basic statistics and vector correlation methods to compare the hourly-averaged HF-Radar current vectors at grid points near the ADCP moorings. Scalar regression analysis yields correlation coefficients (R) of 0.8 to 0.9 for the alongshelf components but 0.6 or less for the cross-shelf components, which are small in magnitude. The alongshelf surface currents measured by the radar are about 30% larger than those of the ADCPs measured 2 to 3 m below the surface according to standard deviations and linear regression slopes. However, a fit of the M2 tide, which is barotropic on the WSF, to the ADCP and radar vector time series yielded current tidal ellipse parameters that are in good agreement, suggesting that the low-frequency, upper-layer shears may be real. The near-surface flow was further explored by examining the wind-driven and Stokes-drift components using both processed vector data and radial speeds.

Submitted on November 21, 2002