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Validating RTOFS Surface Currents with Drifter Trajectories

Validating RTOFS Surface Currents with Drifter Trajectories. Matt Sienkiewicz Department of Marine and Environmental Systems. Why model ocean currents?. Marine forecasts Conduct SAR operations Atmosphere-Ocean coupled hurricane prediction models Forecast oil slick movement. Oil.

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Validating RTOFS Surface Currents with Drifter Trajectories

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  1. Validating RTOFS Surface Currents with Drifter Trajectories Matt Sienkiewicz Department of Marine and Environmental Systems

  2. Why model ocean currents? • Marine forecasts • Conduct SAR operations • Atmosphere-Ocean coupled hurricane prediction models • Forecast oil slick movement Oil MODIS 19 JULY 2010

  3. Loop Current A warm water current that sheds anticyclonic eddies once or twice a year.

  4. Real Time Ocean Forecast System (RTOFS) • Implemented in 2005 • One-day nowcast and 6-day forecast (144 hours) • Curvilinear coordinate system • Based on Hybrid Coordinate Ocean Model (HYCOM) • Covers entire Atlantic basin

  5. RTOFS Coverage GoM: 4-5 km (Mehra and Rivin, 2009)

  6. RTOFS Initialization • Sea surface height – satellite altimetry data • Sea surface temperature – AVHRR • Diurnal and Semi-diurnal tides • River outflow and freshwater flux – USGS • In situ measurements • CTD casts • Argo floats

  7. RTOFS/Drifter Trajectory Analysis • Two drifters deployed in eastern edge of Loop Current • Drifters report lat/lon every hour

  8. Drifter deployment 87803 87806

  9. Drifter Trajectories (10 Jun – 27 Jun) Exit Loop Current

  10. RTOFS Trajectories • Four separate trajectories initialized at actual drifter location at: • Deployment • 14 Jun 00Z • 18 Jun 00Z • 21 Jun 00Z • Trajectories run out to 144th forecast hour, except on 14 Jun (96th hour)

  11. 87803

  12. 87803 27 JUN 2010 24 JUN 2010 16 JUN 2010 18 JUN 2010

  13. 87806 87803

  14. 87806

  15. 87806 24 JUN 2010 24 JUN 2010 16 JUN 2010 18 JUN 2010

  16. R2 = 0.9846

  17. Divergence Analysis • Looking for areas in RTOFS most sensitive to error • Analysis run for entire Gulf of Mexico • Initial time 00Z on 10 Jun 2010 • Run for 120 hours of forecasts 1 1 50km 2 2 3 3 0 0 4 4 Mean distance from center point.

  18. Divergence Analysis (120 hours) Max mean spread: 275.1 km Beginning 10 JUN 2010 00Z

  19. Conclusions • Large errors between drifters and RTOFS for Loop Current • Initial RTOFS placement of drifters outside of Loop Current • Outside edges of current in RTOFS seem more subjected to shear/eddies • Overall RTOFS made a poor display for this analysis in the Loop Current Next Speaker: Cory Hodes

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