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

An atmosphere-ocean coupled regional climate model for the

Mediterranean

Alberto ElizaldeDaniela Jacob

Uwe Mikolajewicz

Max Planck Institute for Meterology

Hamburg, Germany

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

Outline

Motivation & Objectives

Description of the models

Coupling strategy

First experiments of uncoupled models

Summary

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

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

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

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

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

Coupling strategy

AtmosphereModel (REMO)

HydrologicalModel (HD model)

Coupler (OASIS 3)

OceanModel (MPI-OM)

Wind stressFresh water fluxSurface net downward shortwave fluxSurface downward heat fluxWind speed-----------------------------CP: 6H

RunoffDrainage-------------CP: 24H

Discharge-------------CP: 24H

SST----------CP: 6H

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

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

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

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

Experiments

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.

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

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

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

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

Outlook

Setting up of the coupling system

Tests to adjust models parameters

Perform validation of the coupling system

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

Claude Millot, 1997