A coupled high resolution atmosphere-ocean model for the BALTEX region

Abstract

A three-dimensional fully coupled high resolution atmosphere-ocean model for the BALTEX (Baltic Sea Experiment) region has been developed from two independent models, the atmospheric regional model REMO and the Kiel Baltic Sea model. The coupled model was set up in the framework of the BALTEX program to contribute to one of its major objectives, the investigation and quantification of the energy and water cycle in the Baltic Sea and its catchment area. As a first step towards the fully coupled system, sensitivity studies with different forcings for its uncoupled components, the atmosphere and ocean models, were performed. These sensitivity studies demonstrated that both models are able to produce reasonable results which in turn can act as forcing for the respective other model. In the first simulation of the fully coupled system the modeled sea surface temperatures (SST) agree well with satellite observations. Thus they are at least as good as the previously used SSTs from operational analyses and in some cases even better. The detailed evaluation of the coupled model results reveals that often the coupling effects are superimposed by advective influences and that only under specific conditions the atmospheric variables show a remarkable response to different fluxes. The atmosphere-ocean model is coupled directly via the corresponding fluxes across the interface between atmosphere and ocean. For the here presented simulation no flux corrections were necessary. Thus a consistent model system has been developed which can be utilized for further studies of the energy and water cycle in the BALTEX area.