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 analysing 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

Deliverables

D1: Coupled COSMO-CLM/NEMO comprising Mediterranean, North and Baltic Sea
D2: COSMO-CLM/NEMO with coupled river routing scheme
D3: Initalisation 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. One hydrological model was coupled to the ocean-atmosphere system with the European marginal seas.

Initialisation experiments with 20-year simulations were performed and the impact of ocean initial state on the atmosphere was studied.

For investigating the atmospheric lateral boundary conditions (LBCs), an idealized model setup has been established. Different spatial resolutin jumps, temporal update frequencies of the LBCs and two LBC procedures have been tested.

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).