1 / 33

Time Varying OSCAR Surface Currents in the Garbage Patch Regions

Time Varying OSCAR Surface Currents in the Garbage Patch Regions . Kathleen Dohan Earth and Space Research Seattle, WA. OSCAR surface currents.

lucien
Download Presentation

Time Varying OSCAR Surface Currents in the Garbage Patch Regions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Time Varying OSCAR Surface Currents in the Garbage Patch Regions Kathleen Dohan Earth and Space Research Seattle, WA Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  2. OSCAR surface currents • OSCAR surface currents (Ocean Surface Current Analyses- Realtime) are global ocean surface velocities calculated from satellite-sensed SSH, wind, and SST (SSS). • The dataset is produced on a 5-day timebase, on a 1/3 degree regular grid. • Here: • OSCAR currents in the convergent zones • How best to describe the convergent zones? • EulerianvsLagrangian views • Compare with drifters • Effects of vertical variation • Discussion Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  3. OSCAR Surface currents from satellite fields • Ocean Surface Currents Analyses-Realtime processing system (OSCAR) is a satellite-derived surface current database provided in near-real time based on a combination of quasi-steady geostrophic and locally wind-driven dynamics (Bonjean and Lagerloef, 2002). • geostrophic term is computed from the gradient of ocean surface topography fields (AVISO/CLS) • wind-driven velocity components are computed from an Ekman/Stommel formulation with variable eddy viscosity using QuikSCAT vector winds (FSU/COAPS) and NCEP winds • thermal wind adjustment using Reynolds OI SST data. • Data is available at http://podaac.jpl.nasa.gov and http://www.oscar.noaa.gov. • Areas of development: • time-dependent wind-driven dynamics • Turbulent mixing scheme • Vertical variation • Coastal altimetry Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  4. OSCAR Movie Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  5. Validation against drifting buoy velocities • OSCAR surface velocities are interpolated onto drifter locations (which have been averaged over 1 day). Zonal and meridional currents vsdrifter velocities are plotted on the scatter plot. • Drifter data distributed by NOAA/AOML www.aoml.noaa.gov/phod/dac/gdp.html Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  6. OSCAR in the Pacific Vortex Region • OSCAR currents in the Pacific • Snapshot in time • Relatively quiet region Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  7. OSCAR animation Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  8. Variability • Region of low EKE Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  9. Speed • Low mean speed • txt • txt Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  10. Convergent Zones • Simple calculation of w from du/dx and dv/dy Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  11. Convergent Zones Year Average • Simple calculation of w from du/dx and dv/dy Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  12. Convergent Zones Year Average • Transport into the sides of a box around the Pacific patch • Need concentrations of pollutants to connect to garbage patch Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  13. Lagrangian approach: Particles in OSCAR • Simple advection of initial seeding of “drifters” by interpolated currents Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  14. Particles in OSCAR • Final positions after running from 2000 to end of 2009 • Stop when drifters approach coasts (NaN velocities) Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  15. Global Impact of Eddies on Inertial Oscillations of the Mixed Layer Planning Meeting Feb 22-24, 2011

  16. Global Impact of Eddies on Inertial Oscillations of the Mixed Layer Planning Meeting Feb 22-24, 2011

  17. Particles in OSCAR • Drifter paths, color coded by initial position Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  18. Particles in OSCAR • Westward and eastward tracks Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  19. Compare with AOML drifters • Initial position of subset of total drifter array Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  20. Compare with AOML drifters • Final position of subset of total drifter array Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  21. Compare with AOML drifters • Drifter paths (some) Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  22. Compare with AOML drifters • Drifter “end” points are related to concentration of initial deployments • Area binned final locations divided by initial area binning Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  23. Compare with AOML drifters • Amount of time drifter tracks are in bins Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  24. OSCAR • Same plot for OSCAR drifters Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  25. Vertical Variation • Vertical variation is implicit in the OSCAR analytical model. OSCAR currents are averaged over the top 30m of the model. • The wind-driven component in OSCAR uses an eddy viscosity formulation (at the moment), dependent on the wind, with • Optimal choice for a in OSCAR blends from 8 x 10-5 m2s-1, b = 2.2 at the equator as in Santiago-Mandujano & Firing (JPO 1990), to 2.85 x 10-4 m2s-1, b = 2 for the global value. • Following Cronin and Kessler (JPO 2009), we’ve used a vertically varying eddy viscosity which decays with depth (exponential profile), so that stress is zero at depth H. Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  26. Vertical Variation • Green and cyan (OSCAR) show the vertical variation implicit in OSCAR. Blue compares with using a vertically varying eddy viscosity. • Timeseries of averaged 30m currents are compared with TAO mooring data. Less significant for surface measurements, but significant once you are considering transport at varying levels. Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  27. Vertical Variation • Extreme test case of linearly decaying uwith depth to base of mixed layer • Using Holte mixed layer climatology from Argo http://mixedlayer.ucsd.edu • Holte, J., J. Gilson, L. Talley and D. Roemmich, 2010: Argo Mixed Layers, Scripps Institution of Oceanography/UCSD. Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  28. Linearly decaying currents to depth of mixed layer • Lose the convergent zones (albeit unrealistic) Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  29. Vertical Variation • Second test case of surface wind-driven uscaled by depth of mixed layer • U wind = U wind * 30m/MLD • Idea of momentum being distributed over well-mixed layer Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  30. Questions • Are coarse velocity fields enough to measure Lagrangian pathways? • Coasts: we aren’t getting the offshore transport correct (I think) • How reliant are any calculations of transport on the vertical profile? • How deep do particles reside? • How do we quantifiably describe the convergent/divergent zones? • Need concentrations of particles to connect with transport • Turbulent small-scale processes • Vertical processes • Coastal processes • Combine the Lagrangian with Eulerian • Drifters give locations of origin • Transform concentration along coasts into concentrations within convergent regions Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  31. Global Impact of Eddies on Inertial Oscillations of the Mixed Layer Planning Meeting Feb 22-24, 2011

  32. Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

  33. txt • txt • txt • txt Hydrodynamics of Marine Debris” Sunday, March 20, 2011, Honolulu, HI

More Related