1. An atmosphere-ocean coupled regional climate model for the Mediterranean Alberto Elizalde Daniela Jacob Uwe Mikolajewicz Max Planck Institute for Meterology Hamburg, Germany

2. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Outline Motivation & Objectives Description of the models Coupling strategy First experiments of uncoupled models Summary

3. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Motivation & Objectives Assessment of water cycle in the Mediterranean region Better understanding of processes involved Reproduce atmosphere-ocean feedbacks Atmosphere-ocean-hydrological coupling model Analyze the added-value of the coupled system on climate simulations Perform climate change simulations

4. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Model description Atmosphere model REMO - REgional atmosphere Model (Jacob and Podzun, 1997) hydrostatic model Forcing variables: air temperature, wind components, specific humidity, surface pressure and SST 25km 241x145 31 vertical levels

5. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Model description Ocean model MPI-OM – Max-Planck-Institute Ocean Model (Mars-Land et. al, 2002) Regional version for the Mediterranean region Lateral forcing variables: Temperature and salinity Aprox. ~11 km 503x231 29 vertical levels

6. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Model description Hydrological model HD model - Hydrological Discharge model (Hagemann and D¨menil, 1998b) Accounts the lateral waterflow on the land surface Provide to ocean component freshwater input from the surface river system Applied on a regional scale non-rotated spherical grid Resolution: 1/2 ° River mouths

7. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Coupling strategy Atmosphere Model (REMO) Hydrological Model (HD model) Coupler (OASIS 3) Ocean Model (MPI-OM) Wind stress Fresh water flux Surface net downward shortwave flux Surface downward heat flux Wind speed ----------------------------- CP: 6H Runoff Drainage ------------- CP: 24H Discharge ------------- CP: 24H SST ---------- CP: 6H

8. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Coupling strategy Exchange methology: Bilinear interpolation for ocean-atmosphere exchange River mouths are assigned to ocean grid boxes using nearest coast points Reanalysis data to cover none matching areas between both domains Lateral boundary conditions: Reanalysis dataset (ERA40) for the atmospheric component Climatology dataset (Levitus et al., 1998) for the oceanic component

9. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Coupling status Current state of the coupling is on progress Tests of stand-alone version of the models

10. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. MPI-OM – MedAtlas (driving by ERA15) (driving by ERA40) Salinity (psu) and Current Speed (m/s) Experiments Published work: Herrmann M. J. & Somot S. (2008) Claude Millot, 1997

11. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Experiments

12. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Summary The ocean model is able to reproduce Mediterranean Sea circulation, but not when driven by ERA40. Positive bias on precipitation near the northern boundary affects to hydrological cycle that increase moisture values at surface rising values for runoff and drainage, also at low atmosphere moisture is transported to the center of the domain, with a cooling effect. The size and location of the atmospheric domain play an essential roll on coupled simulations. It has a direct impact on water cycle.

13. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy.

16. Outlook Setting up of the coupling system Tests to adjust models parameters Perform validation of the coupling system

17. ESF MedCLIVAR Workshop, 13-15 October, 2008. Trieste, Italy. Claude Millot, 1997