COSTRICE – three model online coupling using OASIS: problems and solutions

Abstract

The coupled system COSTRICE, which contains three component models of atmosphere, ocean and sea ice, was developed to reproduce the interactions and feedback among the atmosphere, ocean and sea ice using a two-way online coupled model system for regional climate simulations of Baltic Sea and North Sea regions. The regional climate model CCLM is coupled with the regional ocean model TRIMNP and the sea ice model CICE via the coupler OASIS3. In this study, CCLM is setup with a horizontal grid mesh size of 50 km and 32 vertical atmosphere layers and is driven by the 6-h ERA-interim re-analysis data as initial and boundary conditions. TRIMNP is constructed with a horizontal grid mesh size of 12.8 km and 50 vertical ocean levels. CICE calculates 5 categories of ice and operates with the same horizontal resolution as TRIMNP, but CICE only simulates the Baltic Sea and Kattegat, a part of the North Sea. In a two-way online coupling process, CCLM is linked to TRIMNP by sea surface temperature (SST) as a lower boundary condition while TRIMNP and CICE are driven by atmospheric state variables and fluxes of CCLM. The coupled system is designed to run in parallel on the supercomputing system IBM-power 6 at the German Climate Computing Centre (DKRZ).