Community Terrain-Following Community Terrain-Following Ocean Modeling System (TOMS)Ocean Modeling System (TOMS)

An overview of the collaboration between the An overview of the collaboration between the modeling communities of Princeton (Ezer) and modeling communities of Princeton (Ezer) and

Rutgers (Arango) to: 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.

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

WorkshopsWorkshops

• First joint terrain-following ocean models users First joint terrain-following ocean models users meeting- meeting- Bar Harbor, ME, 9/1999Bar Harbor, ME, 9/1999– motivated the TOMS/ONR initiative & need for motivated the TOMS/ONR initiative & need for

collaborationcollaboration

• Second joint terrain-following ocean models users Second joint terrain-following ocean models users meeting- meeting- NCAR, CO, 8/2001 NCAR, CO, 8/2001 – Inaugural TOMS developers workshop – 8/2001Inaugural TOMS developers workshop – 8/2001– Second TOMS developers workshop – 7/2003Second TOMS developers workshop – 7/2003

• Third joint terrain-following ocean models users Third joint terrain-following ocean models users meeting- PMEL, Seattle, WA, 8/2003meeting- PMEL, Seattle, WA, 8/2003

Web-based support:Web-based support: communication with the terrain-following communication with the terrain-following

ocean modeling community ocean modeling community

• Improve web-based information at both Improve web-based information at both Princeton (Princeton (http://http://www.aos.princeton.edu/htdocs.pomwww.aos.princeton.edu/htdocs.pom//) ) and Rutgers (and Rutgers (http://http://marine.rutgers.edu/pomarine.rutgers.edu/po//) )

• Launch generic Ocean-Modeling web site (Launch generic Ocean-Modeling web site (http://www.ocean-modeling.orghttp://www.ocean-modeling.org))

Why is this collaboration useful?Why is this collaboration useful?

1.1. Benefit from several developing groups Benefit from several developing groups specializing in different areas (numerics, specializing in different areas (numerics, assimilation, sub grid scale assimilation, sub grid scale parameterizations, etc.)parameterizations, etc.)

2.2. New schemes can be tested by many New schemes can be tested by many different applications running on different applications running on different computer architectures (and different computer architectures (and compared with existing models).compared with existing models).

3.3. Immediate impact on the ocean Immediate impact on the ocean modeling community.modeling community.

A few examples from recent research to A few examples from recent research to evaluate new numerics and evaluate new numerics and

parameterizations:parameterizations:

… and how users may be affected … and how users may be affected

(e.g., model stability and advanced (e.g., model stability and advanced time stepping schemes)time stepping schemes)

Sensitivity to internal (DTI) & external (DTE) time steps Sensitivity to internal (DTI) & external (DTE) time steps (Ezer, Arango & Shchepetkin, 2002)(Ezer, Arango & Shchepetkin, 2002)

DTIDTI

DTEDTE180s180s 360s360s 540s540s 720s720s 900s900s 10801080

ss

8s8s 2222 4545 6767 9090 112112

12s12s 1515 3030 4545 6060 7575

16s16s 2222 3434 4545 5656

20s20s 1818 2727 3636 4545

24s24s 1515 2222 3030 3737

26s26s 1919 2525 3232

32s32s 1717 2222 2828

DTIDTI

DTEDTE180s180s 360s360s 540s540s 720s720s 900s900s 10801080

ss

8s8s 2222 4545 6767 9090

12s12s 1515 3030 4545 6060

16s16s 1111 2222 3434 4545

20s20s 99 1818 2727 3636

ROMS

POM

UNSTABLE

STABLE

TDI/DTE

CFL=13s

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

time steptime step

A recent paper:A recent paper:

A possible explanation for ocean model A possible explanation for ocean model instability occurring for small time instability occurring for small time

stepsstepsB. Heimsund & J. Berntsen, 2003B. Heimsund & J. Berntsen, 2003

try to explain this numerical instability and suggests try to explain this numerical instability and suggests a method to evaluate the stability using a simple a method to evaluate the stability using a simple

shallow water equations on a 3-cell grid shallow water equations on a 3-cell grid

Pressure Gradient SchemesPressure Gradient SchemesSchemeScheme TypeType ReferenceReference

POM-DJPOM-DJ Standard Density Jacobian Standard Density Jacobian schemescheme

Mellor et al. (1998)Mellor et al. (1998)

POM-CCDPOM-CCD Combined Compact Combined Compact Difference scheme (6Difference scheme (6thth))

Chu & Fan (1997)Chu & Fan (1997)

(new HC 2003)(new HC 2003)

ROMS-FPJROMS-FPJ Finite-Volume Pressure Finite-Volume Pressure Jacobian schemeJacobian scheme

Lin (1997)Lin (1997)

ROMS-DJROMS-DJ Weighted Density Jacobian Weighted Density Jacobian scheme (scheme (0)0)

Song (1998)Song (1998)

ROMS-WDJROMS-WDJ Weighted Density Jacobian Weighted Density Jacobian scheme (scheme (0.125)0.125)

Song (1998)Song (1998)

ROMS-PJQROMS-PJQ Pressure Jacobian scheme Pressure Jacobian scheme with Quadratic Polynomial with Quadratic Polynomial fitfit

Shchepetkin & Shchepetkin & McWilliams (2003)McWilliams (2003)

ROMS-DJCROMS-DJC Density Jacobian scheme Density Jacobian scheme with Cubic Polynomial fitwith Cubic Polynomial fit

Shchepetkin & Shchepetkin & McWilliams (2003)McWilliams (2003)

Structure ofStructure ofV (cm/s) in ROMS for different V (cm/s) in ROMS for different PG schemes (medium seamount case)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)

PG errors- moderately steep seamountPG errors- moderately steep seamount

Testing TOMS parallel code (MPI or OpenMP)

for different computer architectures

The cost of saving output and global averaging is much

higher for the MPI code

(for the shared-memory SGI machine)

Related research areas (Princeton group) Related research areas (Princeton group) that can contribute to the TOMS that can contribute to the TOMS

developmentdevelopment• Parameterization of vertical mixing and modification Parameterization of vertical mixing and modification

to the M-Y turbulence scheme:to the M-Y turbulence scheme:

1. 1. Mixing due to internal waves Mixing due to internal waves

(Ezer, 2000; Mellor, 2001)(Ezer, 2000; Mellor, 2001)

2. 2. Surface mixing due to breaking waves Surface mixing due to breaking waves

(Mellor, 2003; Mellor & Blumberg, 2003)(Mellor, 2003; Mellor & Blumberg, 2003)

3.3. Bottom mixing and BBL Bottom mixing and BBL

(Ezer & Mellor, 2003)(Ezer & Mellor, 2003)

Various turbulent mixing schemes in TOMS Various turbulent mixing schemes in TOMS

(Brunt-Vaisala, M-Y-2.5, KPP, Canuto, Kantha-Clayson) (Brunt-Vaisala, M-Y-2.5, KPP, Canuto, Kantha-Clayson) need to be evaluated in view of new research on need to be evaluated in view of new research on turbulence mixing. turbulence mixing.

• Generalized coordinate systemsGeneralized coordinate systems (Mellor et al., 2002; Ezer & Mellor, 2003)(Mellor et al., 2002; Ezer & Mellor, 2003)

help to evaluate future hybrid coordinate systemshelp to evaluate future hybrid coordinate systems • Estuarine, tides, sediment transport, etc. Estuarine, tides, sediment transport, etc.

Experience with POM-related models may help Experience with POM-related models may help in the development and testing of schemes like in the development and testing of schemes like wetting-dryingwetting-drying. .

• Pressure gradient schemesPressure gradient schemes Need to sort the many available schemesNeed to sort the many available schemes

• Operational forecasting systemsOperational forecasting systems

Experience in developing such systems with POM Experience in developing such systems with POM at NOAA & Navy labs can help in the transformation of at NOAA & Navy labs can help in the transformation of TOMSTOMS