1. Coastal Ocean Circulation and biogeochemical modeling
Young-Gyu Park
Korea Ocean Research and Development Institute

2. Pollution Fate & Transport
Mixed with ambient water
How much and how fast?
Transported
How far, how fast and to where?
If you want detailed temporal and spatial distribution, you need a coastal ocean circulation modeling.

3. Ocean Models
Thank to the computer technology, ocean modeling becomes very popular.
Commercial products: coastal engineering
SMS
Public domain: science
POM, ROMS, MOM, HYCOM, COHERENS, FVCOM …
Your own!

4. Is an ocean model a black box?
It is not easy to know all the detail of a 3D ocean circulation model. Even a developer may not know the whole model except the part he/she developed!
Some commercial model could be used as a black box.
In most cases one needs to know the basics at least.

5. Ocean Circulation Model
Decompose the domain into boxes
Grids
Vertical
Horizontal
Transform the continuous hydrodynamic equations into discrete equations
differential difference
Calculate velocity, temperature and salinity at each grid point at certain time.

6. Ocean Circulation Models
Benefit
3D structure of ocean circulation and related fields
Cheap compared to the observations
Parameter (sensitivity) study
Process study
Optimal analysis of observational results
Prediction

7. Ocean Circulation Models
drawback
In some cases, different models produce different results.
Assumptions
Subgrid scale processes: mixing
Hard to justify the assumptions in not a few cases.
Errors
Discretization: Grid size is finite!
Uncertainty in the boundary conditions
Hard to quantify the error in not a few cases.

8. Size of Domain

9. Large scale Ocean Circulation Model
Global ocean, Basin Scale, Climate
MOM (NOAA/GFDL Modular Ocean Model), POP (Parallel Ocean Program), POM (Princeton Ocean Model), HYCOM, ROMS, MRI model, SOC model …
Low horizontal resolution (2-5 degrees)
Cannot resolve major boundary currents properly.
Unphysically large friction to maintain numerical stability

10. Large scale Ocean Circulation Model
Process oriented
Global properties
Global long term prediction
IPCC reports
Global carbon cycle

11. CO2 Exchange (1765) Global Carbon Cycle Model using
MOM and OCMIP CO2 chemistry

12. Regional Ocean Circulation Model
East China Sea, South China Sea
Regional processes
Regional prediction
High horizontal resolution (a few tenth of degree)
Resolve important boundary currents
POM, ROMS, MOM, HYCOM, FVCOM
Open boundary condition

13. East China Sea Model grid for FVCOM

14. High resolution modeling
Earth Simulator in Japan
1/10 degree horizontal resolution

15. Coastal Ocean Circulation Model
Coastal zones and estuary.
Very high resolution (O(10m))
High spatial temporal variability
POM, FVCOM, COHERENS, SMS, ADCIRC …

16. What do we need in a coastal model
Fresh water from rivers and ground water
Tide & intertidal zone
Open boundary: effect of the open ocean
Complex geometry: coast line bottom topography
Higher accuracy

17. Grids (coordinate)

18. Vertical Coordinate
Griffies et al

19. z Coordinate MOM, POP (open ocean) Easy to use
Staircase bottom topography
real
model

20. r (density) Coordinate
HYCOM, HIM (open ocean)
Recently developed
Water moves along isopycnal surfaces
Good physics

21. s Coordinate POM, ROM, FVCOM (regional and coastal ocean)
terrain following
Pressure gradient error
Mellor et al., 1994

22. Generalized (hybrid) vertical coordinate
Overcome inherent limitations in each coordinate system
Z-near surface, s near bottom

23. Horizontal grid
From Chen at UMASSD

24. From Chen at UMASSD

25. 0.5-4 km
4 km
2 km
From Chen at UMASSD

26. Current Popular Numerical Models
1. Finite-Difference Method (the most popular one):
POM (Princeton Ocean Model)
ECOM-si (an updated version of POM)
ROM (developed by the Rutgers University)
Curvilinear coordinate system
2. Finite-Element Method (mainly comes from engineering):
QUODDY (developed by the Dartmouth College)
Unstructured grids (triangular meshes)
From Chen at UMASSD

27. Difference between Finite-Difference, Finite-Element and Finite-Volume Methods (FDM, FEM, FVM)x
Integration
Difference
Variation
From Chen at UMASSD

28. Integration flux method Variational approach
ECOM-si
POM and ROM
Use the central finite-difference scheme for bottom time integration and space gradients;
Two time stepping or mode splitting: a) external mode and b) internal mode;
Time and space smoothing (POM)
Use the semi-implicit scheme to calculate the surface elevation;
Single time stepping
No time and space smoothing
FVCOM
QUODDY
Integration flux method
Variational approach
Models
Pro
Con
Finite-difference
Computational efficiency
Piece-piece structures
Mass conservative (Rectangular grids)
Geometric fitting
Grid-dependent mass conservation
Finite-element
Complicated code structure
Poor mass conservation
Finite-volume
Combine advantage of FDM and FEM
Ensure mass conservation in individual control volume
??????
From Chen at UMASSD

29. Popular models

30. For Large Scale MOM (Modular Ocean Model)
NOAA/GFDL ( z-coordinate
HIM (Hallberg isopycnal model)
NOAA/GFDL ( r-coordinate
HYCOM (HYbrid Coordinate Ocean Model)
Z at the surface, s at the bottom r in the interior

31. POM Princeton Ocean Model
Developed by G. Mellor at the Princeton U.
Global, regional, coastal
It has been very popular, but since G. Mellor’s retirement the model is not being developed anymore.
There are quite a few models originated from POM.
ROMS, ECOM, COHERENS

32. ROMS Regional Ocean Modeling System
Primitive equation s(s)-coordinate model
Actively being developed and maintained.
Global, regional, coastal (?)
Developed by D. Haidvogel at Rutgers U.
Circulation, biogeochemistry, sediment, sea ice

33. FVCOM Finite Volume Coastal Ocean Circulation Model
Unstructured (finite volume) s-coordinate primitive equation hydrostatic model
Developed by Chen and UMASSD and Beardsley at WHOI
Coastal and estuary
Ecosystem, water quality, sediment, sea ice modules

35. Issues in coastal ocean modeling
Open boundary conditions
tide
inflow/outflow and associated tracer transport
Inter tidal zone (wet/dry)
Fresh water flux
Better representation of topography
Mixing
Verification

36. Verification of model results
Observation
Hydrography, satellite …
Model intercomparison

37. Biogeochemical modeling
Nutrient cycle, CO2 cycle, Eco system, Water quality
In some models (ROMS, FVCOM, COHERENS), there are modules for biogeochemical processes.
Interdisciplinary efforts
Physical modelers do not have enough knowledge (or interest) on biogeochemistry.
Biologists or chemists do not believe hydrodynamic model results.

38. Eco system model
Parameters controlling the interaction between the components
1D model: verify the parameters (stability)
Combine with the hydrodynamic model
NPZD model
From FVCOM manual

39. Water Quality Model
From FVCOM manual

40. On going Coastal Ocean Modeling Project in Korea

41. circulation & biogeochemistry
management
circulation &
biogeochemistry
KORDI
Dept. Environment
effect of dyke
circulation &
biogeochemistry
KORDI
management
circulation & biogeochemistry
Under consideration

43. circulation & biogeochemistry
management
circulation &
biogeochemistry
KORDI
Dept. Environment
effect of dyke
circulation &
biogeochemistry
KORDI
management
circulation & biogeochemistry
Under consideration

44. East China Sea Modeling Project
With help from Prof. Chen at UMASSD
Circulation
Eco system

45. Circulation and eco system modeling
Current status
Effects of Yangtze river discharge
Response to the global change
Down scaling from IPCC AR4 simulations

46. Conclusions
A (coastal) ocean circulation model with various modules might become a commodity in a few years irrespective of its inherent flaws and limitations.
It would be very hard to ignore model or model results.
Develop your own or find one serves your purpose best and use it?
One could spend a few years to develop his/her own model, but it is very hard to compete against group efforts.
A model tends to become more and more complex, and it becomes harder to understand the whole model completely, yet we cannot treat the model as a black box.
Collaboration among modelers, chemist, and biologist is crucial, if you want to get useful results.
At KORDI, we are trying to model the circulation and the biogeochemistry of the East China Sea and a few coastal areas.

47. Thank you