1. Community Terrain-Following Ocean Modeling System (TOMS) An overview of the collaboration between the modeling communities of Princeton (Ezer) and Rutgers (Arango) to: Develop, test and improve numerical schemes for terrain-following ocean models in an effort to build an expert, advanced modeling system for wide range of applications. Provide support for the terrain-following ocean modeling community and coordinate the interaction between developers, users and forecasters.

2. TOMS Executive committee Users communities Princeton (POM, NCOM, ECOM) Rutgers/UCLA (SPEM, SCRUM, SEOM, ROMS/TOMS) Others (HYCOM/MICOM, MOM, POP, MIT…) Coordinators Core model development groups Feedback From testers TOMS testers ONR Modeling & Prediction Feedback From intercomparisons with other models

3. Workshops First joint terrain-following ocean models users meeting- Bar Harbor, ME, 9/1999 First joint terrain-following ocean models users meeting- Bar Harbor, ME, 9/1999 –motivated the TOMS/ONR initiative & need for collaboration Second joint terrain-following ocean models users meeting- NCAR, CO, 8/2001 Second joint terrain-following ocean models users meeting- NCAR, CO, 8/2001 –Inaugural TOMS developers workshop – 8/2001 –Second TOMS developers workshop – 7/2003 Third joint terrain-following ocean models users meeting- PMEL, Seattle, WA, 8/2003 Third joint terrain-following ocean models users meeting- PMEL, Seattle, WA, 8/2003

4. Web-based support: communication with the terrain-following ocean modeling community Improve web-based information at both Princeton (http://www.aos.princeton.edu/htdocs.pom/) Improve web-based information at both Princeton (http://www.aos.princeton.edu/htdocs.pom/)http://www.aos.princeton.edu/htdocs.pom/http://www.aos.princeton.edu/htdocs.pom/ and Rutgers (http://marine.rutgers.edu/po/) http://marine.rutgers.edu/po/http://marine.rutgers.edu/po/ Launch generic Ocean-Modeling web site (http://www.ocean-modeling.org) Launch generic Ocean-Modeling web site (http://www.ocean-modeling.org)http://www.ocean-modeling.org

5. Why is this collaboration useful? Why is this collaboration useful? 1. Benefit from several developing groups specializing in different areas (numerics, assimilation, sub grid scale parameterizations, etc.) 2. New schemes can be tested by many different applications running on different computer architectures (and compared with existing models). 3. Immediate impact on the ocean modeling community.

6. A few examples from recent research to evaluate new numerics and parameterizations: … and how users may be affected (e.g., model stability and advanced time stepping schemes) A few examples from recent research to evaluate new numerics and parameterizations: … and how users may be affected (e.g., model stability and advanced time stepping schemes)

7. Sensitivity to internal (DTI) & external (DTE) time steps (Ezer, Arango & Shchepetkin, 2002) DTI DTIDTE180s360s540s720s900s1080s 8s22456790112 12s1530456075 16s22344556 20s18273645 24s15223037 26s192532 32s172228 DTE180s360s540s720s900s1080s8s22456790 12s15304560 16s11223445 20s9182736 ROMS POM UNSTABLE STABLE TDI/DTE CFL=13s

8. While larger time step is possible in ROMS/TOMS, users should be aware of possible oscillatory behavior for small time step

9. A recent paper: A possible explanation for ocean model instability occurring for small time steps B. Heimsund & J. Berntsen, 2003 try to explain this numerical instability and suggests a method to evaluate the stability using a simple shallow water equations on a 3-cell grid

10. Pressure Gradient Schemes SchemeTypeReference POM-DJ Standard Density Jacobian scheme Mellor et al. (1998) POM-CCD Combined Compact Difference scheme (6 th ) Chu & Fan (1997) (new HC 2003) ROMS-FPJ Finite-Volume Pressure Jacobian scheme Lin (1997) ROMS-DJ Weighted Density Jacobian scheme (  0) Song (1998) ROMS-WDJ Weighted Density Jacobian scheme (  0.125) Song (1998) ROMS-PJQ Pressure Jacobian scheme with Quadratic Polynomial fit Shchepetkin & McWilliams (2003) ROMS-DJC Density Jacobian scheme with Cubic Polynomial fit Shchepetkin & McWilliams (2003)

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

12. PG errors- moderately steep seamount

13. Testing TOMS parallel code (MPI or OpenMP) for different computer architectures

15. The cost of saving output and global averaging is much higher for the MPI code (for the shared-memory SGI machine)

16. Related research areas (Princeton group) that can contribute to the TOMS development Related research areas (Princeton group) that can contribute to the TOMS development Parameterization of vertical mixing and modification to the M-Y turbulence scheme: Parameterization of vertical mixing and modification to the M-Y turbulence scheme: 1. Mixing due to internal waves (Ezer, 2000; Mellor, 2001) 2. Surface mixing due to breaking waves (Mellor, 2003; Mellor & Blumberg, 2003) 3.Bottom mixing and BBL (Ezer & Mellor, 2003)  Various turbulent mixing schemes in TOMS (Brunt-Vaisala, M-Y-2.5, KPP, Canuto, Kantha-Clayson) need to be evaluated in view of new research on turbulence mixing.

17. Generalized coordinate systems Generalized coordinate systems (Mellor et al., 2002; Ezer & Mellor, 2003)  help to evaluate future hybrid coordinate systems Estuarine, tides, sediment transport, etc.  Experience with POM-related models may help in the development and testing of schemes like wetting-drying. Estuarine, tides, sediment transport, etc.  Experience with POM-related models may help in the development and testing of schemes like wetting-drying. Pressure gradient schemes Pressure gradient schemes  Need to sort the many available schemes Operational forecasting systems  Experience in developing such systems with POM at NOAA & Navy labs can help in the transformation of TOMS Operational forecasting systems  Experience in developing such systems with POM at NOAA & Navy labs can help in the transformation of TOMS