ScicomP9ScicomP9Bologna, 23 – 26 March 2004Bologna, 23 – 26 March 2004

Wind driven circulation in the Wind driven circulation in the Gulf of Trieste: a numerical Gulf of Trieste: a numerical

study in stratified conditionsstudy in stratified conditions

Querin, S., Crise, A.Querin, S., Crise, A.

Istituto Nazionale di Oceanografia e di Geofisica Istituto Nazionale di Oceanografia e di Geofisica SperimentaleSperimentale

(OGS)(OGS)

Trieste (Italy)Trieste (Italy)

OGS - Dept. Of Oceanology (OGA)OGS - Dept. Of Oceanology (OGA)

ECHO groupECHO group(Ecologic and Hydrodynamic (Ecologic and Hydrodynamic Modeling)Modeling)

• applied hydrodynamics and turbulence modelingapplied hydrodynamics and turbulence modeling

• ecosystem modeling in open sea and coastal areasecosystem modeling in open sea and coastal areas

Short term forecasts for coastal watersShort term forecasts for coastal waters

• environmental protectionenvironmental protection:: coastal ecosystem monitoring and marine protected areas coastal ecosystem monitoring and marine protected areas controlcontrol

Numerical studies and research activity:Numerical studies and research activity:

• operational oceanographyoperational oceanography

• water quality problemswater quality problems:: pollutants transport, oil spill, sewage dischargepollutants transport, oil spill, sewage discharge

Adricosm (ADRIatic sea integrated Coastal areaS Adricosm (ADRIatic sea integrated Coastal areaS and river basin Management system pilot project)and river basin Management system pilot project)

• implementation of an integrated coastal zone management implementation of an integrated coastal zone management system in the Adriatic Seasystem in the Adriatic Sea predictive circulation module: prediction of coastal current variability in Near Real Time predictive circulation module: prediction of coastal current variability in Near Real Time (NRT)(NRT) river basin and wastewater management module: monitoring and modeling of a river river basin and wastewater management module: monitoring and modeling of a river basin andbasin and wastewater system in a test sitewastewater system in a test site

• shelf forecasting system for the Northern Adriatic Sea shelf forecasting system for the Northern Adriatic Sea weeklyweekly forecasts of current dynamicsforecasts of current dynamics

• kkey technical issues:ey technical issues: mmodel (one-way) hierarchical nestingodel (one-way) hierarchical nesting asynchronous coupling of coastal forecasting model and river basin management modelasynchronous coupling of coastal forecasting model and river basin management model prediction optimized by in situ and satellite data assimilationprediction optimized by in situ and satellite data assimilation

• partnerships: Italian, Slovenian, Croatian and French partnerships: Italian, Slovenian, Croatian and French institutionsinstitutions

• project supported by the Italian Ministry for the Environment project supported by the Italian Ministry for the Environment andand TerritoryTerritory

• companion of MFSTEP (mediterranean sea) and companion of MFSTEP (mediterranean sea) and MERSEAMERSEA projectsprojects

Our goals:Our goals:• studying and modeling the dynamics of the Gulf of Trieste studying and modeling the dynamics of the Gulf of Trieste under realistic forcings for short and medium-range forecastsunder realistic forcings for short and medium-range forecasts

• model validation comparing calculated fields with model validation comparing calculated fields with buoy buoy measurements (MAMBO buoys (OGS), NIB’s buoys) and satellite measurements (MAMBO buoys (OGS), NIB’s buoys) and satellite datadata

• embed the code into ADRICOSM structure (embed the code into ADRICOSM structure (improved resolutionimproved resolution: : 250 m)250 m)

The Gulf of Trieste The Gulf of Trieste (GoT)(GoT)

• extensionextension

• bathymetrybathymetry

• prevalent windsprevalent winds

• effects on Adriatic and effects on Adriatic and Mediterranean seaMediterranean sea

Main features of the dynamics in the Gulf of Main features of the dynamics in the Gulf of TriesteTriesteGoT is a ROFI (Region Of Fresh water Influence) area (Simpson, GoT is a ROFI (Region Of Fresh water Influence) area (Simpson, 1997)1997)

The dynamics are governed by:The dynamics are governed by:

• wind stresswind stress

• buoyancy fluxesbuoyancy fluxes

• river inputriver input

• tides & seichestides & seiches

• remote controlremote control

MITgcm novel aspects:MITgcm novel aspects:

• designed to study both atmospheric and oceanic phenomenadesigned to study both atmospheric and oceanic phenomena

• includes non-hydrostatic capability includes non-hydrostatic capability small and large scale small and large scale processesprocesses

• adopts a finite volume technique adopts a finite volume technique treatment of irregular treatment of irregular geometries using orthogonal curvilinear grids and shaved cellsgeometries using orthogonal curvilinear grids and shaved cells

• developed to perform efficiently on a wide variety of developed to perform efficiently on a wide variety of computational platform including MPI parallelizing directivescomputational platform including MPI parallelizing directives

The numerical model:The numerical model:MITgcm Ocean General Circulation ModelMITgcm Ocean General Circulation Model(Marshall et al, 1997)(Marshall et al, 1997)

wnhcc

nh

vc

uc

Fzp1

gDtDw

Fyp1

fuDtDv

Fxp1

fvDtDu

Adjustable Adjustable momentum equationmomentum equation

Non-hydrostatic Non-hydrostatic primitive equation primitive equation modelmodel

Pressure integrationPressure integration

nhsh pppp

hp

sp

nhp

Pressure due to surface elevation (2D)Pressure due to surface elevation (2D)

Hydrostatic pressure (vertical pressure gradient, Hydrostatic pressure (vertical pressure gradient, 2D)2D)

Non-hydrostatic pressure (3D)Non-hydrostatic pressure (3D)

Bottom topography discretization:Bottom topography discretization:

• full cellsfull cells

• piece-wise constant (‘partial’) cellspiece-wise constant (‘partial’) cells

• piece-wise linear (‘shaved’) cellspiece-wise linear (‘shaved’) cells(not yet implemented)(not yet implemented)

• FV can accommodate any type of gridFV can accommodate any type of grid• the grid defines only the control volume boundaries and need the grid defines only the control volume boundaries and need not be related to a coordinates systemnot be related to a coordinates system• the method is conservative by construction: surface integrals the method is conservative by construction: surface integrals which represent convective and diffusive fluxes are the same for which represent convective and diffusive fluxes are the same for the CVs sharing the boundarythe CVs sharing the boundary

Finite volume (FV) techniqueFinite volume (FV) technique

full

partial

shaved

Adopted numerical schemesAdopted numerical schemes

   Pressure Pressure methodmethod

HydrostatHydrostatic/non-ic/non-

hydrostatihydrostaticc

SurfaceSurface Variables Variables in timein time

Time * Time * steppingstepping

11Semi-Semi-

implicitimplicit HydrostaticHydrostatic Rigid lidRigid lid Co-locatedCo-locatedAdams-Adams-

Bashforth Bashforth (AB)(AB)

22Semi-Semi-

implicitimplicit HydrostaticHydrostatic Free Free surfacesurface Co-locatedCo-located

AB\AB\backward backward implicitimplicit

33Semi-Semi-

implicitimplicit HydrostaticHydrostaticRigid lid or Rigid lid or

free free surface surface

StaggeredStaggered (AB)(AB)

44Semi-Semi-

implicitimplicitNon-Non-

hydrostatichydrostatic

Rigid lid or Rigid lid or free free

surface surface Co-locatedCo-located (AB)(AB)

55Semi-Semi-

implicitimplicit HydrostaticHydrostaticNon linear Non linear

free free surfacesurface

Co-located Co-located or or

staggeredstaggered(AB)(AB)

* Horizontal: explicit quasi second order Adams Bashford* Horizontal: explicit quasi second order Adams Bashford Vertical: implicit backward method/Crank-NicholsonVertical: implicit backward method/Crank-Nicholson

Vertical Mixing: KPP profile for ocean interiorVertical Mixing: KPP profile for ocean interiorReference: Large, W.G., McWilliams, J.C. and Doney, S.C., 1994 (Rev. Geophys., 32, 363 - 403)Reference: Large, W.G., McWilliams, J.C. and Doney, S.C., 1994 (Rev. Geophys., 32, 363 - 403)

Processes :Processes :

• resolved shear instability mixingresolved shear instability mixing

• unresolved shear instability due to internal wave fieldunresolved shear instability due to internal wave field

• double diffusiondouble diffusion

Parameterization of diffusivity and viscosity:Parameterization of diffusivity and viscosity:

zθ

w'θ' θ

zS

'S'w S

z

''w m

v

v

swd

dws w

ms

mm dS

wS

sSS

parameterized in terms of gradient Richardson numberparameterized in terms of gradient Richardson number

constant (Peters constant (Peters et al.et al., 1988; Large , 1988; Large et al.et al., 1994), 1994)

function of double diffusion density ratiofunction of double diffusion density ratio

Vertical Mixing: KPP profile for surface boundary layerVertical Mixing: KPP profile for surface boundary layer

Processes :Processes :

• wind driven mixingwind driven mixing

• surface boundary fluxessurface boundary fluxes

• convective instabilityconvective instability

θθ γzθ

Kw'θ'

sS γzS

Kw'S'

z

K''w mv

v

Parameterization of diffusivity and viscosity:Parameterization of diffusivity and viscosity:

G : polinomial functionG : polinomial function

hhb b : boundary layer : boundary layer thicknessthickness

Surface boundary layer thickness: minimum depth at which bulk Richardson number Surface boundary layer thickness: minimum depth at which bulk Richardson number exceeds the criticalexceeds the critical

Richardson number RiRichardson number Ricc=0.3=0.3

Reference: Large, W.G., McWilliams, J.C. and Doney, S.C., 1994 (Rev. Geophys., 32, 363 - 403)Reference: Large, W.G., McWilliams, J.C. and Doney, S.C., 1994 (Rev. Geophys., 32, 363 - 403)

σ Gσ whhhσK iibbi

ParameterizationParameterization

AAhh 4 4 ÷ ÷ 40 m40 m22/s/s

AAvv constant (or KPP profile) constant (or KPP profile) 10 m10 m22/s/s

KKhh 4 4 ÷÷ 40 m 40 m22/s/s

KKvv constant (or KPP profile) constant (or KPP profile) 4 4 ÷÷ 10 m 10 m22/s/s

Goals:Goals:• wide range of phenomena wide range of phenomena • wide range of platformswide range of platforms• high computational high computational performanceperformance

Architecture:Architecture:• core numerical codecore numerical code• “ “pluggable” packagespluggable” packages• support framework: support framework: WRAPPER WRAPPER (WRappable (WRappable Application Parallel Programming Application Parallel Programming Environment Resource)Environment Resource)

Software ArchitectureSoftware Architecture

Communication primitivesCommunication primitivesDomain decomposition (2D)Domain decomposition (2D)

Parallel Parallel implementationimplementation

Domain decomposition (3D)Domain decomposition (3D)

Speed-up:Speed-up:

parallel

sequential

)usertime(

)usertime(3,5 with 4 processors3,5 with 4 processors

5,8 with 8 processors5,8 with 8 processors

9,8 with 16 processors9,8 with 16 processors

Use of up to 16 processors with a domain decomposition Use of up to 16 processors with a domain decomposition characterized by 4 x 4 spatial boxescharacterized by 4 x 4 spatial boxes

PerformancePerformance (IBM SP4 computer at CINECA)

• f-plane, 250 m spatial resolutionf-plane, 250 m spatial resolution

• 30° rotation for domain optimization30° rotation for domain optimization

• integration domain: 88 x 128 x 25integration domain: 88 x 128 x 25

• 25 (1 m thick) levels25 (1 m thick) levels

• bathymetry:bathymetry: linear kriging interpolationlinear kriging interpolation no filtering proceduresno filtering procedures small manual adjustmentssmall manual adjustments

• I.C.:I.C.: derived from MAMBO buoy profiles derived from MAMBO buoy profiles

• B.C.:B.C.: adiabaticadiabatic lateral free-sleeplateral free-sleep quadratic bottom frictionquadratic bottom friction open/closed boundary conditionsopen/closed boundary conditions

Design of the numerical experiments for the Gulf of Design of the numerical experiments for the Gulf of TriesteTrieste

Initial conditions:Initial conditions:MAMBO (Monitoraggio AMBientale Operativo) buoy MAMBO (Monitoraggio AMBientale Operativo) buoy data setdata set

Time/depth Hovmoller diagram of parameters measured by Time/depth Hovmoller diagram of parameters measured by MAMBO buoyMAMBO buoy

Depth dependent temperature and salinity profilesDepth dependent temperature and salinity profiles

Layout of numerical Layout of numerical experimentsexperiments

wind type time [day] output frequency4 bora 2 h

8=4 bora+4no wind 2 h8=4 bora+4no wind 2 h

4bora 1 h4 bora 2 h4 bora 1 h4 bora 1 h

8=4 bora+4no wind 2 h8=4 bora+4almost zero 2h7.5=4bora+4almostzero 2h

30 bora 1 day128 time steps 6 s

4 libeccio 1 h4 libeccio 2 h

SCIROCCO 4scirocco 2 hKPP profile constant wind 40

KPP profile shear wind 40KPP profile constant wind 40

LIBECCIO 10 m/sKPP profile shear wind 40KPP profile constant wind 4

KPP profile shear wind 40KPP profile constant wind 40

KPP profile shear wind 40KPP profile constant wind 40BORA 14 m/s

Kv constant constant wind 40KPP profile constant wind 4KPP profile constant wind 40

BORA 10 m/sKPP profile constant wind 4KPP profile constant wind 4KPP profile constant wind 40

SIMULATIONS: WIND DRIVEN CIRCULATIONGULF of TRIESTE - Stratified I.C.

Kv constant/KPPprofile constant/shear wind kh [m2/s]

Averaged wind regime in Trieste Averaged wind regime in Trieste during the period 1991-2000 during the period 1991-2000 (after Stravisi)(after Stravisi)

Wind driven upwelling in the GoT during a Bora Wind driven upwelling in the GoT during a Bora episodeepisode(28-29 July 2003)(28-29 July 2003)

Wind driven upwelling in the GoT during a Bora Wind driven upwelling in the GoT during a Bora episodeepisode(28-29 July 2003)(28-29 July 2003)

ETA 1/6° LAM ETA 1/6° LAM

Model: 29/07/03 Model: 29/07/03

06.00 GMT06.00 GMT

U10m U10m

NOAA-12 AVHRR NOAA-12 AVHRR Sea Surface Sea Surface TemperatureTemperature

Temperature after 3 days of boraTemperature after 3 days of bora

Constant bora:Constant bora:14 m/s14 m/swind stress curl = 0wind stress curl = 0

Meridionally sheared bora:Meridionally sheared bora:14 - 7 m/s14 - 7 m/swind stress curl > 0wind stress curl > 0

Vertical sectionVertical section

KPP profile - 8 days (4 Bora + 4 no wind)KPP profile - 8 days (4 Bora + 4 no wind)

Constant boraConstant bora Sheared boraSheared bora

Wind driven circulationWind driven circulationCoexistence of mixing and upwelling phenomena: a proof using a Large-Eddy Coexistence of mixing and upwelling phenomena: a proof using a Large-Eddy SimulationSimulation

18 °C

22 °C

BuoyBuoy measurementsmeasurements

Model resultsModel results

Results Results

• application of the model to a real case studyapplication of the model to a real case study

• good qualitative match with experimental observations good qualitative match with experimental observations

• successful implementation on a parallel environmentsuccessful implementation on a parallel environment

Ongoing work Ongoing work

• nesting with larger model (active BC)nesting with larger model (active BC)

• ‘ ‘realistic’ wind forcing (2.5 km spatial resolution)realistic’ wind forcing (2.5 km spatial resolution)

• Isonzo river input dynamicsIsonzo river input dynamics

• buoyancy fluxesbuoyancy fluxes

Real-time oceanographic forecastsReal-time oceanographic forecasts