Overview and Applications Ramon Margalef Summer... · Simulation models: are used for calculating realistic circulation of oceanic regions. The ﬁrst simulation models were developed

OverviewGeneral Circulation Models vs. Regional Models

ROMS modelROMS applications

Ocean numerical modelsOverview and Applications

Jordi Solé i Ollé

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Índice

1 Overview

2 General Circulation Models vs. Regional ModelsGeneral Circulation ModelsRegional Models (RM)

3 ROMS model

4 ROMS applicationsAnalytical applications (test cases)ESPreSSOPhilexCBLAST (Coupled Boundary Layers and Air-Sea Transfer)Alboran Sea

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Índice

1 Overview


3 ROMS model


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Índice

1 Overview


3 ROMS model


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Índice

1 Overview


3 ROMS model


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Conceptual diagram

Lynch et al. 20093 / 54



Conceptual diagram

Lynch et al. 20094 / 54



Main conceptual issues

1 Encourage the use of probabilistic model results mean and varianceand the expression of this in simple ways to a general audience,backed by rigorous analysis.

2 Encourage the formalization of the best prior estimate at the least,the mean and variance of all relevant prior quantities.

3 Always examine the posterior: a) the remaining misfit and b) thedeparture from the prior. There is information in both.

4 Ensemble modeling approaches, specifically the use of anensemble of different models, are appealing in the context ofoperational physical-biological models.

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Main practical issues

1 It is essential to facilitate access to real-time data streams. Thisincludes networking, servers, and people

2 Encourage communication and interaction between data providersand modeling activities.

3 Similarly, encourage partnership between physical modeling andbiological modeling.

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Main organizational issues

1 Recognize the importance of organizational structure. Encourageregional expertise in regional centers; and networking of theserelative to technical and scientific generalities.

2 Encourage a blend of Government/University/Industrial activity.3 Use the existing centers and cooperative programs to their fullest.

There is much opportunity in these for cross-fertilization. Avoidcreating new organizations if extant ones can be made to work.

4 Recognize the importance of small steps toward a larger goal.5 Focus on system integration of models, theory, and observation as

an overarching goal.

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Conceptual diagram

Lynch et al. 20098 / 54



General Circulation ModelsRegional Models (RM)

Contents

1 Overview


3 ROMS model


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Global Ocean Models (GOM)

Generally speaking there are thre kinds of models:

Mechanistic models: they are simplified models used and orientedfor studying processes.Simulation models: are used for calculating realistic circulation ofoceanic regions. The first simulation models were developed by KirkBryan and Michael Cox at the Geophysical Fluid Dynamicslaboratory in Princeton.Coupled Atmosphere and Ocean numerical models: Ocean modelsrun 30 times slower than atmosphere models of the samecomplexity.

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GOM (II)

GOM main characteristics. Vertical resolution is typically around 30vertical levels. Models include

Realistic coasts and bottom featuresHeat and water fluxes though the surfaceEddy dynamicsThe meridional-overturning circulation

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GOM (II)



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GOM (II)



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GOM (II)



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GOM (II)

Instantaneous, near-surface geostrophic currents in the Atlantic for October 1, 1995(POP, Parallel Ocean Program model) http://oceanworld.tamu.edu/resources/

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GOM (III)

GOM models have Z vertical coordinates.

Daily Mean Analysis Fields from 26 jan 2010 at 12:00 for NEMO model.

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Contents

1 Overview


3 ROMS model


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Also known as Coastal Models:

The models extend from the beach to the continental slope, andthey can include a free surface, realistic coasts and bottom features,river runoff, and atmospheric forcing.They have σ-coordinates in the vertical:

S(x , y , σ) = hcσ + (h(x , y)− hc)C(σ) (1)

They need additional information about deep-water currents orconditions at the shelf break

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S(x , y , σ) = hcσ + (h(x , y)− hc)C(σ) (1)


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S(x , y , σ) = hcσ + (h(x , y)− hc)C(σ) (1)


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RM (II)

North Atlantic Vtransform=2, Vstretching=2, θs = 7.0, θb = 0.1, N=30.

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RM (III)

Finite difference models

Sub-grid turbulence is parameterized using a closure schemeproposed by Mellor and Yamada (1982) whereby eddy diffusioncoefficients vary with the size of the eddies producing the mixingand the shear of the flow.The model is driven by wind stress and heat and water fluxes frommeteorological models. The model uses known geostrophic, tidal,and Ekman currents at the outer boundary.The model has been used to calculate the three-dimensionaldistribution of velocity, salinity, sea level, temperature, andturbulence for up to 30 days over a region roughly 100-1000 km on aside with grid spacing of 1-50 km.

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RM (III)



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RM (III)



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RM (IV)

Finite element models3-dimensional model of the circulation using a triangular,finite-element grid. The size of the triangles is proportional to bothdepth and the rate of change of depth. The triangles are small inregions where the bottom slopes are large and the depth is shallow,and they are large in deep water. The variable mesh is especiallyuseful in coastal regions where the depth of water varies greatly.Thus the variable grid gives highest resolution where it is mostneeded.The model has a simplified equation of state and a depth-averagedcontinuity equation, and it uses the hydrostatic and Boussinesqassumptions. Sub-grid mixing of momentum, heat and mass isparameterized using the Mellor and Yamada (1982)turbulence-closure scheme.

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RM (IV)

Finite element models3-dimensional model of the circulation using a triangular,finite-element grid. The size of the triangles is proportional to bothdepth and the rate of change of depth. The triangles are small inregions where the bottom slopes are large and the depth is shallow,and they are large in deep water. The variable mesh is especiallyuseful in coastal regions where the depth of water varies greatly.Thus the variable grid gives highest resolution where it is mostneeded.The model has a simplified equation of state and a depth-averagedcontinuity equation, and it uses the hydrostatic and Boussinesqassumptions. Sub-grid mixing of momentum, heat and mass isparameterized using the Mellor and Yamada (1982)turbulence-closure scheme.

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RM (V)

Finite elements models

Topographic map of the Gulf of Maine. Inset: Triangular, finite-element grid used tocompute flow in the gulf. The size of the triangles varies with depth and rate of change of

depth. From Lynch et al. (1996).

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RM (IV)

Some currently used RM

HOPS (Harvard Ocean PredictionSystem.http://modelseas.mit.edu/HOPS/)POM (Princenton Ocean Model.http://www.aos.princeton.edu/WWWPUBLIC/htdocs.pom/)HYCOM (Hybrid Coordinates Ocean Model. http://www.hycom.org/)SEOM (Spectral Element Ocean Model.http://marine.rutgers.edu/po/index.php?model=seom)ROMS (Regional Ocean Model System. www.myroms.org)

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RM (IV)



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RM (IV)



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RM (IV)



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RM (IV)



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ROMS (Regional Ocean Modeling System)

http://www.myroms.org

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Contents

Introduction to ROMS physical circulation modelROMS coupling: physical-biological models, circulation-sedimenttransport, wave model-circulation model, sea-ice model-circulationmodel.Data assimilation in ROMS

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Contents


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Contents


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ROMS model

free surface, hydrostatic primitive equations model interrain-following coordinates3rd-order upstream-biased advection (Shchepetkin and McWilliams,1998)pressure gradient and equation of state give reduced s-coordinatetruncation error (Shchepetkin and McWilliams, 2003a)split-explicit time-stepping of barotropic and baroclinic modesconstrained for conservation of volume and tracer constancy(Shchepetkin and McWilliams 2003b)radiation open boundary conditions and 1-way embedding inexterior model domains (Marchesiello et al. 2001)

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ROMS model


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ROMS model


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ROMS model


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ROMS model


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ROMS model II

synchronous Lagrangian particle trackingvertical turbulence closures: KPP (Large et al. 1994) and theGeneralized Length Scale scheme of Umlauf, and Burchard, 2003(http://www.gotm.net) encompassing k-e, k-w and Mellor-Yamada(1982)intermittent sub-optimal melding assimilationtangent linear and adjoint codes written; 4DVar assimilation indevelopment (Moore et al. 2003)atmospheric, oceanic, and benthic (wave and current) boundarylayers (Styles and Glenn)coupled ecosystem (7-component NPZD and EcoSim bio-optics)and sediment transport (USGS Community Model) modules

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ROMS model II


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ROMS model II


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ROMS model II


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ROMS model II


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ROMS model II


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ROMS model III

The data assimilation:Try to use the measured data to improve the model resultsThere are two main methods to do data assimilation: EnsembleKalman Filter and Variational methodsROMS has implemented a variational method

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ROMS model III


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ROMS model III


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ROMS model IV

The data 4DVAR method:

It is based in three parts: Forward model, tangent linear model andadjoint modelForward model is the full model running all the equations as it isTangent linear model: the linearisation of the non-linear (forward)modelAdjoint model: the time-backwards model calculated from thethagent linear model.

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ROMS model IV



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ROMS model IV



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ROMS model IV



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ROMS model V: 4DVAR

Fig. from http://www.ecmwf.int/newsevents/training/

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Analytical applications (test cases)ESPreSSOPhilexCBLAST (Coupled Boundary Layers and Air-Sea Transfer)Alboran Sea

Contents

1 Overview


3 ROMS model


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Upwelling

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Upwelling II: Results

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Cape

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Cape II: results

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Contents

1 Overview


3 ROMS model


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Experimental System for Predicting Shelf and SlopeOptics

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Espresso

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Contents

1 Overview


3 ROMS model


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Philipines Archipielago Straits

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Philipines Archipielago Straits

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Contents

1 Overview


3 ROMS model


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To provide useful forecasts of the regional heat budget south ofMartha’s Vineyard, ROMS should capture the essential features ofthe 3-dimensional heat transport on diurnal to several daytime-scales, and spatial scales of order 1 kmTo achieve this, we have employed a high degree of realism in theconfiguration of model bathymetry and forcing. The present modelhas fine grid spacing (1 km) and realistic bathymetry from theNGDC Coastal Relief Model, active/passive inflow/outflow openboundaries (Marchesiello et al. 2001) incorporating a bi-monthlyclimatology of shelf circulationThe 160 x 380 resolution grid with 20 vertical levels requiresapproximately 2 CPU mins per model day on 16-processorHPCompaq Alphaserver.

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CBLAST II

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Contents

1 Overview


3 ROMS model


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Alboran Sea

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Alboran Sea I

Study and identify global change scenarios in the Mediterraneanbasin and subasins and their impact on the inter-annual variability ofthe ecosystem.To study the contribution of mesoscale and sub-mesoscaleinterdisciplinary processes to 3d upper ocean inter-annual variabilityin the Mediterranean Sea.

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Alboran Sea I

Study and identify global change scenarios in the Mediterraneanbasin and subasins and their impact on the inter-annual variability ofthe ecosystem.To study the contribution of mesoscale and sub-mesoscaleinterdisciplinary processes to 3d upper ocean inter-annual variabilityin the Mediterranean Sea.

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Alboran Sea II

Structure of the implementation

2 km horizontal resolution grid (260x150) with 30 vertical levelsBoundary conditions from NEMO GCM model. Atmospheric forcingfrom ERA-40 ECMWF.Biological plankton model: Fasham model (NPZD)

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Alboran Sea II



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Alboran Sea II



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Alboran Sea III

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Alboran Sea IV

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Alboran Sea V

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Conclusions

Regional models are useful tools to understand or study differentkind o foceanic phenomena.ROMS is a system that has a physical regional model coupled toother models or applications.The model has a broad spectra of applications, from the help todesing oceanographic campaigns to remote sensors imagereconstruction.

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Conclusions


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Conclusions


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Documents

Overview and Applications Ramon Margalef Summer... · Simulation models: are used for calculating realistic circulation of oceanic regions. The ﬁrst simulation models were developed