Presentation on theme: "L. K. Shay, J. Martinez-Pedraja , A. B. Parks"— Presentation transcript:
1 L. K. Shay, J. Martinez-Pedraja , A. B. Parks Application of High Frequency Radar & Okubo-Weiss Parameter to Analyze Variability in the Florida CurrentOcean Sciences 2012Matthew ArcherL. K. Shay, J. Martinez-Pedraja , A. B. Parks
2 [Source: http://oceancurrents.rsmas.miami.edu] Florida Current[Source:Gulf StreamIMPORTANCE – MOC/heat transport + wind driven gyre circulation. Previous research focused mainly on explaining this larger scale variability.LoopCurrentDrifter Trajectories between
3 Florida Current Meanders Cyclonic eddies; Florida Atlantic Ocean ⌐ Bahamas¬CubaFlorida KeysCal Say BankSantaren Channel Gulf of MexicoNW Providence ChannelSouthBightMeandersCyclonic eddies;Tortugas eddies (TE)Frontal eddies (FE)Submesoscale motions…IMPORTANCE – MOC/heat transport + wind driven gyre circulation. Previous research focused mainly on explaining this larger scale variability.
4 Vortices in the Florida Current Shay et al., 1998; Shay et al., 2000 ; Parks et al., 2009Shay et al.  ; Shay et al.  ; Parks et al. ForcingAbrupt wind changeLength Scale2-30 km (cross-shelf)4-40 km (along-shelf)Translational Velocitykm/dayRotation-Cyclonic-Dipole excited by near-inertial wave propagationVortices research
5 ObjectivesUsing high frequency (HF) radar as tool to monitor the evolution of the Florida Current, for:Oil spill mitigation procedures in the surface layerSearch and Rescue (Cuban Rafters)Larvae transportOptimizing commercial shipping interests (i.e. going with the flow)FOCUSTo understand the surface current signals associated with energetic vortices to improve real time monitoring across the FC in addressing the above issues.
7 WEllen RAdar (WERA) Specifications Frequency Modulated Continuous Wave (FMCW) System:Chirp Interval: 0.26 secOperating frequency: MHzRange: 80 kmHorizontal resolution: 1.2 kmSampling interval: 10 minFlexible: can be altered to sample a few minutes to several hours (e.g. 128, 256, 512……samples in the averaging)
8 In Florida Current velocities often exceed 200 cm s-1 AccuracyTotal radial accuracy~ 3-5 cms-1In Florida Current velocities often exceed 200 cm s-1ADCP Comparison:[14-m bin depth Vs. radar cell]Complex correlation ~ 0.8ADCP MooringAdapted from Parks et al. 
11 Spatial Dimensions ~30-km Along-Shelf ≈ 17-km Cross-Shelf ≈ 24-km Peters et al., 2002:Radius of Deformation in the Florida Straits shelf break:~30-km
12 = 46 km/day u-component velocity Slope ̴ 66 km/34 hrs Wind Shift Cold FrontWind ShiftAdapted from Parks et al., JGR Wind Stress calculation following Fairall et al., JGR 
13 Okubo-Weiss (OW) Criterion Based on the eigenvalues of the velocity gradient tensor. Physically it describes the balance between vorticity and deformation:OW = Sn Ss ω2Normal StrainShear StrainVorticityRefer to: McWilliams ; Isern-Fontanet et al. [2003; 2004; 2006] ; Chelton et al. ; Chaigneau et al. 
17 Summary: Work In progress WERA resolves submesoscale features.Marked bin to bin coherence in the surface signals.Several years of data sensing the FCRegarding 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.Need to change this – put future work at the very end (or very start) not just in the middle!Frequency analysis to determine forcing mechanisms?
18 Future WorkSubsurface structure from ADCP suggests barotropic nature over the shelf break – relationship to the topography and bottom boundary layer?Relationship to the wind stress fieldFrequency decompositionParks et al., JGR