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Matthew Archer

Application of High Frequency Radar & Okubo-Weiss Parameter to Analyze Variability in the Florida Current. Ocean Sciences 2012. Matthew Archer. L. K. Shay, J. Martinez-Pedraja , A. B. Parks. www.rsmas.miami.edu/users/marcher. Florida Current. Gulf Stream. Loop Current.

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Matthew Archer

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  1. Application of High Frequency Radar & Okubo-Weiss Parameter to Analyze Variability in the Florida Current Ocean Sciences 2012 Matthew Archer L. K. Shay, J. Martinez-Pedraja , A. B. Parks www.rsmas.miami.edu/users/marcher

  2. Florida Current Gulf Stream Loop Current [Source: http://oceancurrents.rsmas.miami.edu] Drifter Trajectories between 1978 - 2003

  3. Florida Current South Atlantic Bight Florida Atlantic Ocean • Meanders • Cyclonic eddies; • Tortugas eddies (TE) • Frontal eddies (FE) • Submesoscale motions… ⌐ Bahamas¬ NW Providence Channel Florida Keys  Gulf of Mexico Cal Say Bank Santaren Channel Cuba

  4. Vortices in the Florida Current Shay et al., 1998; Shay et al., 2000 ; Parks et al., 2009 Shay et al. [1998] ; Shay et al. [2000] ; Parks et al. [2009]

  5. Objectives • Using high frequency (HF) radar as tool to monitor the evolution of the Florida Current, for: • Oil spill mitigation procedures in the surface layer • Search and Rescue (Cuban Rafters) • Larvae transport • Optimizing commercial shipping interests (i.e. going with the flow) • FOCUS • To understand the surface current signals associated with energetic vortices to improve real time monitoring across the FC in addressing the above issues.

  6. Radar Site ADCP mooring (80-m depth) CMAN Buoy

  7. WEllenRAdar (WERA) Specifications Frequency Modulated Continuous Wave (FMCW) System: • Chirp Interval: 0.26 sec • Operating frequency: 16.045 MHz • Range: 80 km • Horizontal resolution: 1.2 km • Sampling interval: 10 min Flexible: can be altered to sample a few minutes to several hours (e.g. 128, 256, 512……samples in the averaging)

  8. Accuracy Total radial accuracy ~ 3-5 cms-1 In Florida Current velocities often exceed 200 cm s-1 ADCP Comparison: [14-m bin depth Vs. radar cell] Complex correlation ~ 0.8 ADCP Mooring Adapted from Parks et al. [2009]

  9. Case Study: Submesoscale Vortex January 2005

  10. Spatial Dimensions Along-Shelf ≈ 17-km Cross-Shelf ≈ 24-km Peters et al., 2002: Radius of Deformation in the Florida Straits shelf break: ~30-km

  11. u-component velocity Slope ̴ 66 km/34 hrs = 46 km/day Wind Shift Cold Front Adapted from Parks et al., JGR [2009] Wind Stress calculation following Fairall et al., JGR [1996]

  12. Okubo-Weiss (OW) Criterion • Based on the eigenvalues of the velocity gradient tensor. Physically it describes the balance between vorticity and deformation: OW = Sn2+ Ss2- ω2 Normal Strain Shear Strain Vorticity Refer to: McWilliams [1984]; Isern-Fontanet et al. [2003; 2004;2006] ; Chelton et al. [2007]; Chaigneauet al. [2008]

  13. Application of OW

  14. Application of OW

  15. Application of OW

  16. Summary: Work In progress • WERA resolves submesoscale features. • Marked bin to bin coherence in the surface signals. • Several years of data sensing the FC • Regarding implementation of Okubo-Weiss … Jury is still out on using OW given importance of shear and strain along the western flank of the Florida Current and its impact on submesoscale structures.

  17. Future Work • Subsurface structure from ADCP suggests barotropic nature over the shelf break – relationship to the topography and bottom boundary layer? • Relationship to the wind stress field • Frequency decomposition Parks et al., JGR [2009]

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