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Xiaochun Wang

Tide Simulation Using Regional Ocean Modeling System (ROMS). Xiaochun Wang. Co-author: Changming Dong, Yi Chao, Zhijin Li, James McWillams. Contributions from: Koji Matsumoto, John Farrara, Jei-kook Choi, Quoc Vu. ROMS/TOMS Workshop Oct. 24-26 2005. Three Level Nested ROMS.

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Xiaochun Wang

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  1. Tide Simulation Using Regional Ocean Modeling System (ROMS) Xiaochun Wang Co-author: Changming Dong, Yi Chao, Zhijin Li, James McWillams Contributions from: Koji Matsumoto, John Farrara, Jei-kook Choi, Quoc Vu ROMS/TOMS Workshop Oct. 24-26 2005

  2. Three Level Nested ROMS 3-Level Nested Model Grid Size Time Step Res. L1: 85*170*32 900s 17km L2: 95*191*32 300s 6km L3: 83*179*32 100s 2km 16 Processors on SGI Altix 3000 1 hour integration takes 1min cpu time.

  3. Boundary Conditions • Open Boundary Condition SSH: Chapman condition Tangential Barotropic Velocity: Oblique radiation Normal Barotropic Velocity: Flather condition • Closed Boundary Condition SSH: Zero gradient Tangential Velocity: Free slip Normal Velocity: Zero Tide SSH and transport are from the barotropic tide data assimilation system of Oregon State University (TPXO.6). Atmospheric Forcing: Hourly wind stress and heat flux.

  4. Tide Solution in Nested ROMS (M2) Tide constituents used: M2 K1 O1 S2 N2 P1 K2 Q1

  5. Comparison with T/P Tide Estimation Away from the coast Courtesy of Dr. Koji Matsumoto (Japan)

  6. Comparison with Tide Gauges (Amp) RSS: 5.41cm M2 K1 O1 S2 N2 P1 K2 Q1 RMS 4.59 1.29 0.92 2.00 0.64 0.93 0.54 0.29 Coastal region, 10 stations.

  7. Comparison with Tide Gauges (Phase) M2 K1 O1 S2 N2 P1 K2 Q1 Blue: Tide Gauge Green: ROMS M2 K1 O1 S2 N2 P1 K2 Q1 RMS 3.42 2.39 3.75 4.06 2.53 5.10 3.08 7.28

  8. Comparison with Tide Gauges RMS of one month sea surface height from model and 10 tide gauges.

  9. Comparison around Monterey Bay Monterey Bay 3 Gauges L1 Domain 10 Gauges Three stations: Moss Landing, Santa Cruz, Monterey Bay

  10. Nested Tide Solution for One Station Tide solution is improved in finer resolution model domain.

  11. Quadratic Bottom Drag Coefficient 3.e-3 1.e-3 30e-3 100e-3 Tide Solution is more robust in OGCMs than in barotropic models.

  12. Future Plan • Tidal Data Assimilation Find optimal boundary condition • Tidal Current Simulation How to improve the tide current

  13. Summary • Forced by tidal signal along the open boundaries in west, north and south directions, ROMS can simulate tide reasonably well for US west coast region. • Comparing with barotropic tide models, the tide simulation is not sensitive to bottom drag coefficient in ROMS. • Addition of tide into ROMS is a significant step toward an operational ocean forecasting system of the region.

  14. Tide Current Estimation • Tide current changes with stratification • Missing data • Subtidal current influence Sheme: The data is 8-28-hour band-pass filtered to remove the subtidal signal. When the length of missing data is less than 12 hours, a linear interpolation is used to fill the gap. When the missing data is longer than 12 hours, the longest segment of data is used to estimate tide current ellipses.

  15. Tide Current:A long journey with a humble beginning HF Radar Surface Current ROMS Surface Current

  16. Stratification (M1 Mooring) August, September, October 2003

  17. HF Radar Tidal Current (M2) 2003 August September October Tidal current is sensitive to stratification

  18. Tidal Current (M1 ADCP) August October 2003 September Tidal current is sensitive to stratification

  19. Spatial Comparison (M2 K1 O1 S2) ROMS SSH TPXO (SSH) M2 K1 K1 M2 O1 O1 S2 S2

  20. Spatial Comparison (Vbar) ROMS TPXO

  21. Spatial Comparison (Ubar) ROMS TPXO

  22. RMS of ROMS (L1) and TPXO SSH Ubar Vbar Difference of SSH is small. Difference of transport is large.

  23. Influence of Bottom Drag Coefficient 0 3*10^-4 30*10^-4 Linear Case 300*10^-4 Compared with barotropic tidal models, the ROMS tidal solution is not sensitive to Bottom Drag Coefficient (<300*10^-4).

  24. Influence of Boundary Condition Tidal Solution is a combined effect of boundary conditions.

  25. Tide in ROMS and TPXO(M2)

  26. Comparison with Tide Gauges (Amp) RSS: 5.41cm RSS: 2.72cm Coastal region

  27. Comparison with Tide Gauges (Phase) M2 K1 O1 S2 N2 P1 K2 Q1 Blue: Tide Gauge Green: ROMS Red: TPXO

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