C1-WP1 - Interactive European marginal seas

Project aims

This work package improves the representation of the marginal seas in the regional decadal prediction system for Europe based on COSMO-CLM (CCLM). During MiKlip, regional forecasting experiments with interactively coupled regional ocean-atmosphere models have shown that an active ocean component improves the simulations compared to atmosphere-only simulations (e.g., West African monsoon simulations). This added value will be investigated further by analyzing and improving the initial- and lateral boundary conditions for the coupled ocean-atmosphere model (CCLM with ocean model NEMO) and by introducing a river runoff scheme to close the hydrological cycle. With these studies the understanding of the high-resolution interactions between ocean, atmosphere and land surface will be improved, the coupled regional modeling system will allow representing more regional feedback mechanisms, and the single-model atmosphere-only CCLM ensemble for regional decadal predictions will be augmented with an additional physics perturbation member for the regional hindcast ensemble.

Project structure

This work package C1-WP1 is handled by the Goethe University Frankfurt (GUF) in co-operation with DWD.

Tasks of the project

There are five sub-tasks:

  • Coupling marginal seas within one modeling system
  • Closing the water cycle/river discharge
  • Initialization and lateral boundary conditions of marginal seas
  • Atmospheric lateral boundary conditions
  • Testing and system set-up


D1: Coupled COSMO-CLM/NEMO comprising Mediterranean, North and Baltic Sea
D2: COSMO-CLM/NEMO with coupled river routing scheme
D3: Initalization procedure for the marginal seas

Progress so far

Ocean models for the major European marginal seas, the North- and Baltic seas as well as the Mediterranean Sea, have successfully been coupled to the atmospheric model in one modeling system.

To close the water cycle, two hydrological models have been tested. Work is ongoing to produce a numerically stable system with at least one of the hydrological models.

Initialization experiments with 20-year simulations were performed. The impact of ocean initial state on the atmosphere is studied.

For investigating the atmospheric lateral boundary conditions, an idealized model setup has been established, which is currently used to test the default and a new LBC procedure.

Coupled regional simulation results were published for Baltic Sea (Pham et al.,2016) and Mediterranean Sea (Akhtar et al., 2017). Furthermore, mesoscale Mediterranean wind systems have been studied (Obermann et al., 2016 and Obermann-Hellhund et al., 2017).



Institut für Atmosphäre und Umwelt Goethe University Frankfurt/Main
Bodo Ahrens
+49 69 798-40244

Anika Obermann
+49 69 798-40234

Mistral and Tramontane wind systems in climate simulations from 1950 to 2100

2017 - Climate Dynamics

Obermann-Hellhund, A. | D. Conte, S. Somot, C. Zsolt Torma, and B. Ahrens

Climate Modeling over the Mediterranean Sea: Impact of Resolution and Ocean Coupling

2017 - Climate Dynamics

Akhtar, N. | J. Brauch and B. Ahrens

Simulation of snowbands in the Baltic Sea area with the coupled atmosphere-ocean-ice model COSMO-CLM/NEMO

2017 - Met. Zeitschrift, Vol. 26(1) , pp. 71 - 82

Pham, v. T. | J. Brauch, B. Früh, and B. Ahrens

Long term evolution of the heat budget in the Mediterranean Sea from Med-CORDEX forced and coupled simulations

2016 - Clim. Dynamics.

Harzallah A. | G. Jordà, C. Dubois, G. Sannino, A. Carillo, L. Li, T. Arsouze, J. Beuvier, and N. Akthar

Influence of Sea Surface Roughness Length Parameterization on Mistral and Tramontane Simulations

2016 - Advances in Science and Research, Vol. 13, pp. 107-112

Obermann, A. | B. Edelmann, and B. Ahrens