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Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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- 146 -<br />

Comparis<strong>on</strong> of Simulati<strong>on</strong>s with the Atmosphere-Only Regi<strong>on</strong>al Climate<br />

Model REMO against Simulati<strong>on</strong>s with the Fully Coupled Regi<strong>on</strong>al<br />

Climate Model System BALTIMOS<br />

Philip Lorenz and Daniela Jacob<br />

Max-Planck-Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany; email: philip.lorenz@dkrz.de<br />

1. Introducti<strong>on</strong><br />

A major task of the BALTic Sea EXperiment (<strong>BALTEX</strong>) is<br />

to simulate the water and energy cycle of the Baltic Sea<br />

catchment to identify important processes, which are<br />

relevant to the climate in the Baltic regi<strong>on</strong>.<br />

A fully coupled regi<strong>on</strong>al climate model system for the Baltic<br />

Sea regi<strong>on</strong>, called BALTIMOS, was developed in the<br />

framework of DEKLIM/<strong>BALTEX</strong> by linking existing model<br />

comp<strong>on</strong>ents for the atmosphere, for the ocean including sea<br />

ice, for the hydrology as well as for lakes. With this system<br />

it is possible to model the complete water and energy cycle<br />

for the Baltic catchment for today’s climate; as well as for<br />

the future with climates szenarios.<br />

The emphasis of this presentati<strong>on</strong> is <strong>on</strong> the descripti<strong>on</strong> of the<br />

model system and <strong>on</strong> the comparis<strong>on</strong> of the results of the<br />

fully coupled BALTIMOS system against the results of the<br />

atmosphere <strong>on</strong>ly model REMO for today’s climate.<br />

2. The DEKLIM-project BALTIMOS<br />

Figure 1. Integrati<strong>on</strong> of sub-projects within the<br />

BALTIMOS project<br />

DEKLIM is the German Climate Research Programme<br />

(2001 – 2006) funded by the Federal Ministry of Educati<strong>on</strong><br />

and Research (BMBF). Within DEKLIM there is a project<br />

called “BALTIMOS” which has the objective to develop<br />

and validate a coupled model system for the Baltic regi<strong>on</strong>.<br />

Nine german instituti<strong>on</strong>s are participating; two of them for<br />

the development and the others for the validati<strong>on</strong> of the<br />

coupled model system. The linking between these subprojects<br />

of BALTIMOS is shown in figure 1.<br />

3. Descripti<strong>on</strong> of the coupled model system<br />

The coupled model system c<strong>on</strong>sists of the following highresoluti<strong>on</strong><br />

comp<strong>on</strong>ents:<br />

REMO: regi<strong>on</strong>al atmospheric climate model. The used<br />

horiz<strong>on</strong>tal resoluti<strong>on</strong> is 1/6° (~ 18 km) with 20<br />

vertical levels. The model domain covers the<br />

whole drainage basin of the Baltic Sea as well<br />

as major parts of Europe.<br />

BSIOM: regi<strong>on</strong>al ocean model for the Baltic Sea<br />

including a sea-ice comp<strong>on</strong>ent. The horiz<strong>on</strong>tal<br />

resoluti<strong>on</strong> is 5 km with 60 vertical levels<br />

LARSIM: hydrological model with lateral transport<br />

scheme; horiz<strong>on</strong>tal resoluti<strong>on</strong> is identical to<br />

REMO; the model domain is the drainage<br />

basin of the Baltic Sea.<br />

The coupling time step between all comp<strong>on</strong>ents is <strong>on</strong>e<br />

hour.<br />

4. Comparis<strong>on</strong> of coupled vs. uncoupled<br />

simulati<strong>on</strong>s<br />

In order to estimate the added value of the above described<br />

coupled regi<strong>on</strong>al model system, multi year simulati<strong>on</strong>s of<br />

both the BALTIMOS system and the “uncoupled” (standal<strong>on</strong>e)<br />

atmosphere <strong>on</strong>ly model REMO have been carried<br />

out.<br />

Both simulati<strong>on</strong>s are driven at the atmospheric lateral<br />

boundaries with ECMWF analysis data. In the uncoupled<br />

run the sea surface temperature (SST) and ice surface<br />

temperature (IST) analysed by ECMWF are prescribed;<br />

while in the coupled run SST and IST are provided by the<br />

ocean/sea-ice model BSIOM.<br />

The atmospheric results of these simulati<strong>on</strong>s will be<br />

compared against each other. Also comparis<strong>on</strong>s of the<br />

results with atmospheric observati<strong>on</strong>s will be presented as<br />

far as reas<strong>on</strong>able.<br />

References<br />

Bremicker, M.: Das Wasserhaushaltsmodell LARSIM;<br />

Modellgrundlagen und Anwendungsbeispiele,<br />

Freiburger Schriften zur Hydrologie, Band 11, 2000<br />

Jacob, D., U. Andrae, G. Elgered, C. Fortelius, L. P.<br />

Graham, S. D. Jacks<strong>on</strong>, U. Karstens, Chr. Koepken, R.<br />

Lindau, R. Podzun, B. Rockel, F. Rubel, H.B. Sass,<br />

R.N.D. Smith, B.J.J.M. Van den Hurk, X. Yang: A<br />

Comprehensive Model Intercomparis<strong>on</strong> <str<strong>on</strong>g>Study</str<strong>on</strong>g><br />

Investigating the Water Budget during the <strong>BALTEX</strong>-<br />

PIDCAP Period, Meteorology and Atmospheric<br />

Physics, Vol.77, Issue 1-4, pp. 19-43, 2001<br />

Jacob, D.: A note to the simulati<strong>on</strong> of the annual and interannual<br />

variability of the water budget over the Baltic<br />

Sea drainage basin, Meteorology and Atmospheric<br />

Physics, Vol.77, Issue 1-4, pp. 61-73, 2001<br />

Lehmann, A. and Hinrichsen, H.-H.: On the thermohaline<br />

variability of the Baltic Sea, J. Marine Systems, Vol.<br />

25, Issue 3-4, pp. 333-357, 2000

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