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Model Evaluation Studies for Improved Ocean Models - TOMS Inaugural Meeting

This meeting, held on August 23, 2001 at NCAR, focused on comparing numerical elements in ocean models to enhance code development and user choices. The goal was to evaluate different schemes and parameterizations in POM and ROMS/TOMS based on criteria such as accuracy, stability, and computational cost.

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Model Evaluation Studies for Improved Ocean Models - TOMS Inaugural Meeting

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  1. TOMS Inaugural Meeting, NCAR, Aug. 23, 2001 Model Comparison and Evaluation Studies Tal Ezer (with H. Arango & A. Shchepetkin)

  2. Goal: to evaluate and test new numerical elements in terrain-following ocean models. • Why: to help developers in improving codes and users in selecting options and parameterizations. • How: by comparing different schemes and parameterizations in POM and ROMS/TOMS. • Criteria: numerical errors, accuracy, stability, compatibility between schemes, computational cost.

  3. Tested Elements • Advection schemes • Time stepping algorithms • Pressure gradient schemes • Others

  4. Seamount configuration test Very steep case h=4050m, w=50km s=0.36, r=14.2 moderately steep h=2700m, w=100km s=0.07, r=2.7 S=max(DH/2H) r=max(sDH/HDs) grid=(64x64x20), Dx=8km

  5. Zonal flow -50cm 0 +50cm Topography Sea surface height

  6. Effect of advection scheme on model: Surface elevation anomaly ADV2- 2nd ord. cnt. POM ROMS ADV4- 4th ord. cnt. ADV3- 3rd ord. upst. ROMS ROMS

  7. Time-stepping schemes(split mode: baroclinic/internal and barotropic/external)

  8. Coupling of barotropic (external) and baroclinic (internal) modes in ROMS weights Un+1 = SamUm Un+½ = S bm’Um’ DTE 1<m<N, N=DTI/DTE DTI

  9. Sensitivity to internal (DTI) & external (DTE) time steps ROMS UNSTABLE STABLE TDI/DTE POM CFL=13s

  10. Computational cost for different models & parameterizations

  11. The adjustment process in POM and ROMS: forced case (zonal flow)

  12. Roms- sensitivity of adjustment procesto time step choices DTE=12s DTE=24s DTI=360s DTI=720s

  13. Pressure Gradient Schemes

  14. Structure ofV (cm/s) in ROMS for different PG schemes (medium seamount case) R-DJ (Vmax=3.7) R-PJQ (Vmax=0.03) R-FPJ (Vmax=30) R-DJC (Vmax=0.06) R-WDJ (Vmax=0.3)

  15. PG errors- moderately steep seamount

  16. More model elements and schemes need to be tested • Boundary conditions • Data assimilation • Nesting and air-sea coupling • Horizontal and vertical mixing schemes • Generalized coordinate system: comparisons between sigma, z-level & isopycnal grids.

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