1. Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas Physical and Biogeochemical Coupled Modelling Presented by Christel PINAZO Mediterranean University Oceanographic Center of Marseille Physical & Biogeochemical Oceanographic Laboratory

2. Introduction Why use Coupled Models ? Historical considerations Different types of Coupled Models Box models Fine grid Models (1D, 2D and 3D) Different ways of Coupling Models « Off-line » Coupling « On-line » Coupling Examples LECTURE SCHEDULE

3. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES THE STUDY SITE COULD BE SPATIALLY DESCRIBED BY FINE MESH GRID IN 1D, 2D OR 3D

4. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES TO CALCULATE THE VARIATION OF BIOGEOCHEMICAL CONCENTRATIONS : - EQUATION OF TEMPERATURE VARIATION OF THE HYDRODYNAMIC MODEL

5. Time evolution COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES 1D FINE GRID MODEL (VERTICAL) SEDIMENT z=-h z=0  z Vertical eddy diffusivity Vertical advection Settling Velocity Concentration Trend term= Sources – Sinks

6. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES ADVANTAGES: FINE DISCRETISATION ONLY ALONG VERTICAL AXIS SIMULATION OF VERTICAL EDDY DIFFUSIVITY (MIXED LAYER) AND UP OR DOWNWELLING PHENOMENA RELATIVE SHORT COMPUTATIONAL TIME LONG SIMULATION OF SEASONS OR YEARS DISADVANTAGES: NOT SIMULATE HORIZONTAL ADVECTION NOT SIMULATE CORIOLIS EFFECT 1D FINE GRID MODEL (VERTICAL)

7. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES 2D FINE GRID MODEL (HORIZONTAL) depth-integrating Navier-Stokes equations O x y Time evolution Horizontal advection Horizontal eddy diffusivity Concentration Trend term= Sources – Sinks

8. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES ADVANTAGES: DISCRETISATION ONLY ALONG HORIZONTAL AXES SIMULATION OF HORIZONTAL ADVECTION AND DIFFUSIVITY SIMULATION OF CORIOLIS EFFECT MEAN COMPUTATIONAL TIME SIMULATION OF MONTHS OR SEASONS DISADVANTAGES: NOT SIMULATE VERTICAL EDDY DIFFUSIVITY (MIXED LAYER) NOT SIMULATE UP OR DOWNWELLING PHENOMENA NOT SIMULATE SEVERAL-LAYERS 2D FINE GRID MODEL (HORIZONTAL)

9. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES 3D FINE GRID MODEL Navier-Stokes equations Time evolution 3D advection 3D eddy diffusivity Concentration Trend term= Sources – Sinks O x y z

10. COUPLING TYPES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES>FINE COUPLING WAYS EXAMPLES ADVANTAGES: FINE DISCRETISATION ALONG THE 3D AXES SIMULATION OF ALL THE MAIN PHENOMENA DISADVANTAGES: RELATIVE LONG COMPUTATIONAL TIME SHORT SIMULATION OF FORTNIGTH TO MONTHS 3D FINE GRID MODEL

11. Introduction Why use Coupled Models ? Historical considerations Different types of Coupled Models Box models Fine grid Models (1D, 2D and 3D) Different ways of Coupling Models « Off-line » Coupling « On-line » Coupling Examples LECTURE SCHEDULE

12. COUPLING WAYS Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTION COUPLING TYPES COUPLING WAYS EXAMPLES 2 DIFFERENT COUPLING WAYS : - OFF-LINE : 2 SEPARATED RUNS WITH PHYSICAL FORCING CONDITIONS STORED IN FILES - ON-LINE : DIRECT AND DYNAMIC COUPLING IN 1 RUN

13. Introduction Why use Coupled Models ? Historical considerations Different types of Coupled Models Box models Fine grid Models (1D, 2D and 3D) Different ways of Coupling Models « Off-line » Coupling « On-line » Coupling Examples LECTURE SCHEDULE

14. OFF-LINE COUPLING Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES COUPLING WAYS>OFF-LINE EXAMPLES dt= 600 s Hydrodynamic Model MARS 3D Wind Tide Physical Forcing Variables : Currents Eddy diffusivity Surface elevation… Irradiance River inputs Wastewater inputs Ecological Model Eco3M dt= 1 hour dt= 1200 s Ecological trends Physical Forcing dt = 50 s Spatial and temporal evolution Of biogeochemical variables Advection Diffusion Biogeochemical variables

15. DIRECT AND DYNAMIC COUPLING Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTIONCOUPLING TYPES COUPLING WAYS>ON-LINE EXAMPLES Irradiance River inputs Wastewater inputs Ecological Model dt= 1 hour dt= 1200 s Ecological trends dt= 600 s Hydrodynamic Model Wind Tide Physical Variables : Currents Surface elevation… dt= 50 s Advection Diffusion variables bio Spatial and temporal evolution Of biogeochemical variables

16. EXAMPLES Regional Advanced School on Physical and Mathematical Tools for the study of Marine Processes of Coastal Areas INTRODUCTION COUPLING TYPES COUPLING WAYS EXAMPLES 3D coupled physical and biogeochemical Modelling Study of ecosystem functioning Of the SW lagoon of New Caledonia

17. Study site description

18. Nord West wind Trade winds Study site

19. Study Site

20. Vitesse, m s -1 Direction, 360° Data from PhD thesis S. Jacquet (2005) Wind measurements (îlot Maître) Dumbéa river Inputs Débit, m 3 s -1  High short-term variability of meteorological forcings  Low seasonal variability Study site

21. Model description

22. horizontal mesh grid: 500m Nb horizontal cells: 340*90 10 vertical sigma levels Forcings : wind, tides Mars3D IFREMER-IRD (P. DOUILLET) Ecological Model: 170*90 Horizontal cells Physical Modelling ECO3M

23. Surface currents: Trade winds 8 m s -1 NOUMÉA Physical Modelling

24. Current Model C and N Cycles 12 variables Zooplankton = « forcing function » Eco3M tool Ecological Modelling

25. Phytoplankton biomass measurements Chl.a Phytoplankton biomass modelling CarbonNitrogen …. ? Constant ratio Carbon : Chlorophyll a Chl.a : diagnostic variable calculated from other state variables Chl.a : Dynamic state variable But: Faure et a (2006) Ecological Modelling

26. Irradiance River inputs Wastewater inputs Ecological Model Eco3M (LOB) dt= 1 hour dt= 1200 s Ecological trends dt= 600 s Hydrodynamic Model MARS 3D (IFREMER-IRD) Wind Tide Physical Variables : Currents Surface elevation… dt= 50 s Advection Diffusion variables bio Spatial and temporal evolution Of biogeochemical variables Dynamic coupling between the 2 models

27. Model results

28. Irradiance Débit des rivières Vent Measured forcings Field measurements : HIVER 2003

29. Realistic Simulation

30. Chla, µg l -1 19 June 3 July Weak Trade windsWeak West wind Realistic Simulation : HIVER 2003, 2D Results

31. Chla, µg l -1 3 July 15 July West windTrade Winds Realistic Simulation : HIVER 2003, 2D Results

32. Chla, µg l -1 15 July 26 July Trade Winds and rainfall Realistic Simulation : HIVER 2003, 2D Results

33. Chla, µg l -1 26 July 7 August West windTrade winds Realistic Simulation : HIVER 2003, 2D Results