The Hybrid Ocean Modeling Environment (HOME)
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The Hybrid Ocean Modeling Environment (HOME) A vision for Community Ocean Circulation Models: Generalized Vertical Coordinates. Presented on behalf of the HOME Team: R. Hallberg, R. Bleck, E. Chassignet, R. deSzoeke, S. Griffies, P. Schopf, S. Springer and A. Wallcraft.

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Presented on behalf of the home team

The Hybrid Ocean Modeling Environment (HOME)A vision for Community Ocean Circulation Models:Generalized Vertical Coordinates

Presented on behalf of the HOME Team:

R. Hallberg, R. Bleck, E. Chassignet, R. deSzoeke, S. Griffies, P. Schopf, S. Springer and A. Wallcraft


Presented on behalf of the home team

The HOME white paper advocates:

  • Development: A versatile, open-source, community Ocean Modeling Environment using a generalized hybrid vertical coordinate.

  • Science: Study best practices for modeling various important oceanic phenomena.


The 10 year vision

The 10-year Vision

  • Precursor ocean models disappear.

  • Artificial fault lines of ocean modeling community based on vertical coordinate (r vs. Z vs. s) are erased.

  • The same ocean modeling codes usable for education, research, and operations.

  • Open, international, and multi-disciplinary.


What is a modeling environment

What is a “Modeling Environment”?

A “Model”:

  • A specific collection of algorithms –e.g. MICOM v2.8

    - or -

  • A specific configuration, including parameter settings, geometry, forcing fields, etc. –e.g. The 1/12° North Atlantic MICOM model

    A “Modeling Environment”:

  • Uniform code comprising a diverse collection of interchangeable algorithms and supporting software from which a model can be selected.


What are hybrid coordinates

What are hybrid coordinates?

σ-z

z

σ

Hybrid


Presented on behalf of the home team

There is broad agreement among ocean modelers that generalized vertical coordinates are desirable.A large fraction of the U.S. ocean model development community will therefore participate in HOME development.

  • HOME Predecessor Models:

    • HIM (NOAA/GFDL)

    • HYCOM (U. Miami, Navy NRL, & DOE LANL)

    • HYPOP (DOE LANL)

    • Poseidon (NASA/GMAO & George Mason U.)

    • POSUM (Oregon State U.)

  • Contributing Models:

    • MITgcm (MIT) – A. Adcroft

    • MOM4 (NOAA/GFDL) – S. Griffies

    • ROMS (Rutgers U. & UCLA) – D. Haidvogel, J. McWilliams, A. Shchepetkin


Presented on behalf of the home team

Examples of HOME predecessor model applications:Studies of the role of resolution and eddies in climate variability


Examples of home predecessor model applications tropical instability waves in an enso forecast

Examples of HOME predecessor model applications:Tropical Instability Waves in an ENSO forecast


Presented on behalf of the home team

Examples of HOME predecessor model applications:1/12° Pacific HYCOM with regional nesting

Forced with high frequency ECMWF winds and thermal forcing

SSH Snapshot – 21 March


Examples of home predecessor model applications mediterranean overflow into an atlantic model

Examples of HOME predecessor model applications:Mediterranean Overflow into an Atlantic Model


Examples of home predecessor model applications global climate simulations at nasa giss

Examples of HOME predecessor model applications:Global climate simulations at NASA/GISS


Presented on behalf of the home team

HOME would be a joint effort of several Federal Agencies (NOAA, Navy/NRL, NASA, DOE) and university groups, with a structure that invites contributions from the broader domestic and international community.

HOME could be construed to partially address Rec. 28-2 of the U.S. Commission on Ocean Policy Report:

“NOAA and the U.S. Navy should establish a joint ocean and coastal information management and communications program… [that] should create a research and development component…to generate new models and forecasts in collaboration with Ocean.IT, taking full advantage of the expertise found in academia and the private sector.”


Advantages of home community cohesion

Advantages of HOME: Community Cohesion

  • An organic trust-base already exists within the Lagrangian-vertical-coordinate ocean modeling community.

  • All major developers recognize the practical benefits from trading “code ownership” for “community modeling”

    • Reduced redundancy of efforts

    • Increased collaborations and intellectual cross-fertilization

    • Increased capabilities available to all researchers and applications

    • More rapid solution of common difficulties


Advantages of home ingenuity

Advantages of HOME: Ingenuity

  • More rapid model improvements

  • Combine existing capabilities of predecessor models to identify optimal configurations

  • Provide a target for new developments to be rapidly evaluated and transitioned to realistic ocean model applications.

  • Enable direct comparison of new techniques with existing in idealized and actual applications

    Biological metaphor: “Breed” better ocean models from a bigger “gene pool” of algorithms.


Advantages of home technology

Advantages of HOME: Technology

ESMF or PRISM Superstructure

  • Built upon ESMF & PRISM standards

  • Single code-base readily deployable to a wide variety of computer architectures

  • Facilitates long-term support & stability

  • ESMF adoption provides a window of opportunity when the transition to HOME will be less disruptive.

Selected

HOME Code

ESMF Infrastructure

(Low-level utilities)

External Hardware libraries, MPI, NetCDF, …


Advantages of home technology1

Advantages of HOME: Technology

ESMF or PRISM Superstructure

  • Built upon ESMF & PRISM standards

  • Single code-base readily deployable to a wide variety of computer architectures

  • Facilitates long-term support & stability

  • ESMF adoption provides a window of opportunity when the transition to HOME will be less disruptive.

AGCM

Selected

HOME Code

ESMF Infrastructure

(Low-level utilities)

External Hardware libraries, MPI, NetCDF, …


Advantages of home education

Advantages of HOME: Education

  • Students would learn about using ocean models with the same code-base as is widely used for real applications.

  • The HOME code will allow for easy-to-use, pedagogically interesting examples.

  • Code will be adaptable for a wide variety of student research topics.


A science vision

A Science Vision

  • IPCC-class climate simulations

  • Biogeochemical simulations

  • Pelagic-to-coastal integration

  • Ocean data assimilation


Home and climate modeling

HOME and Climate modeling

  • Hybrid-isopycnal coordinate HOME-predecessor models are being used for IPCC at NASA/GISS and NOAA/GFDL.

    • Most coupled climate models have traditionally used Z-coordinates, leading to common biases.

    • Multiple types of viable climate models will be enormously powerful for evaluating robustness.

  • Dense overflows mediate many climatically important slow processes (e.g. North Atlantic thermohaline circulation). Controlling the level and location of diapycnal diffusion in overflows is of particularly importance for long climate simulations.

  • Eddy-permitting models using Z-coordinates exhibit large advective diapycnal watermass modification (Griffies et al., MWR, 2000). Isopycnal coordinates may prove uniquely useful for eddy-permitting climate simulations.


Presented on behalf of the home team

Physical-Biogeochemical Model: Fei Chai

Air-Sea

Exchange

Small

Phytoplankton

[P1]

Micro-

Zooplankton

[Z1]

Biological

Uptake

Total CO2

[TCO2]

Grazing

NO3

Uptake

NH4

Uptake

Predation

Nitrate

[NO3]

Excretion

Meso-

Zooplankton

[Z2]

Ammonium

[NH4]

Fecal

Pellet

Advection

& Mixing

N-Uptake

Fecal

Pellet

Grazing

Lost

Silicate

[Si(OH)4]

Detritus-N

[DN]

Detritus-Si

[DSi]

Si

Uptake

Diatoms

[P2]

Physical

Model

Sinking

Sinking

Sinking


Home and biogeochemical modeling

HOME and Biogeochemical modeling

Biogeochemical modeling places unique demands on ocean models:

  • Use lots of tracers

    • Typically evolve more slowly than internal gravity waves

    • The HOME techniques allow very clean separation of tracer time stepping from dynamics.

    • GFDL/HIM is ~10 times faster than GFDL/MOM4 in 1° global models with 20 tracers and same number of layers!

  • Depend strongly on material conservation of properties

    • Isopycnal coordinate models ability to control diapycnal diffusion is invaluable.


Presented on behalf of the home team

Examples of HOME predecessor model applications:

1/25° East Asian Seas HYCOM (nested inside 1/6° Pacific)

North-south velocity cross-section along 124.5°E, upper 400 m

blue=westward flow

red=eastward flow

density front

associated with

sharp topographic feature

(cannot be resolved with

fixed coordinates)

Isopycnals over

shelf region

Yellow Sea flow

reversal with depth

Snapshot on14 October

z-levels and sigma-levels

over shelf and in mixed layer

East China

Sea

Snapshot on

12 April

Yellow

Sea


Presented on behalf of the home team

HYCOM

The hybrid coordinate in HYCOM is isopycnalin the open stratified ocean, but smoothly reverts to a terrain-following coordinate in shallow coastal regions, and to a pressure coordinate in the mixed layer and/or unstratified seas.


Coastal applications of home

Coastal applications of HOME

  • HOME predecessor models already work in coastal applications

  • HOME offers the prospect of moving from the blue-water into the coastal zones seamlessly.

  • Nesting, open boundary conditions, and data assimilation capabilities have been used successfully.

  • Key coastal model developers (J. McWilliams, D. Haidvogel, A. Shchepetkin) have agreed to collaborate in making world-class HOME-based coastal models.


Home and ocean data assimilation

HOME and Ocean Data Assimilation

  • Several HOME predecessors have demonstrated value from multiple data assimilation approaches.

    • Optimal Interpolation ; EnVOI ; EnKF ; SEEK ; ROIF ; Adjoint

  • HOME will be a natural host for this collection of methodologies.

  • Some data assimilation techniques require a tangent linear model and adjoint of the forward model, which can be naturally incorporated in the framework.


The 10 year roadmap

The 10-year Roadmap

  • Distinct HOME predecessor codes disappear within 3-5 years.

  • HOME group will have extensive consultation with European and other international counterparts (e.g. NEMO)

  • Strong coordination with existing Z- and s- modeling groups over 3-5 years sets the stage for next step.

  • Broad unification of all ocean model development activities within a generalized ocean modeling environment over 10 years.

  • Algorithmic diversity will persist, with the selection dictated by the needs of specific applications.


Home measures of success 1

Voluntary participation of existing isopycnal & hybrid ocean model community in developing a common ocean modeling environment.

Collaboration from the broader ocean model development community, especially in the extension of HOME to applications that have not traditionally used isopycnal coordinates.

Contributions of new capabilities from beyond the circle of developers of existing models.

HOME Measures of Success (1)


Home measures of success 2

A code base that is easy to configure and use for a variety of applications, with clear, consistent, and explicit documentation

Widespread adoption of the HOME code-base for ocean applications

Useful and extensive best-practice guidance for HOME users

Pedagogically useful examples derived from the HOME code base

HOME Measures of Success (2)


Presented on behalf of the home team

  • -Rotating and stratified fluids=>dominance of

  • lateral over vertical transport.

  • -Hence, it is traditional in ocean modeling to orient

  • the two horizontal coordinates orthogonal to the

  • local vertical direction as determined by gravity.

  • -The choice of the vertical coordinate system is the

  • single most important aspect of an ocean model's

  • design (DYNAMO, DAMÉE-NAB).

  • -The practical issues of representation and

  • parameterization are often directly linked to the

  • vertical coordinate choice(Griffies et al., 2000).


Why does the vertical coordinate matter so much

Why does the vertical coordinate matter so much?

  • Properties of the ocean:

    • Hydrostatic

    • Adiabatic

    • Rotating and density stratified

    • Surface forced

    • Constrained by bathymetry

      Consequences: Conservative of PV, tracers, momentum, etc.

  • The vertical coordinate strongly affects the ability of a numerical model to respect these properties, and to parameterize unresolved physical processes.


Presented on behalf of the home team

Currently, there arethree main vertical coordinates

in use, none of which provides universal utility.

Hence, many developers have been motivated to

pursue research intohybrid approaches.


Presented on behalf of the home team

Currently, there arethree main vertical coordinates

in use, none of which provides universal utility.

Hence, many developers have been motivated to

pursue research intohybrid approaches.


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