A model-measurements comparison of atmospheric forcing and surface fluxes of the Baltic Sea

Observed basic meteorological quantities, heat and radiation fluxes from three different measurement stations in the Baltic Sea are compared with model data of the coupled sea-ice-ocean model BSIOM in order to evaluate the atmospheric forcing, corresponding surface fluxes and the sea surface response. Observational data weremade available from the BASIS winter campaigns in 1998 and 2001 as well as from the r/v ‘Alkor’ cruise in June 2001. Simulated fluxes were calculated from prescribed atmospheric forcing provided from the SMHI meteorological database and modelled sea surface temperatures. The comparison of these fluxes with observations demonstrates a strong correlation, even though mean differences in sensible heat fluxes range from 4 to 12 W m−2 in winter and −25 W m−2 in the June experiment. Differences in latent heat fluxes range from −10 to 23 W m−2. The short-wave radiation flux used as model forcing is on average 15 W m−2 less than the corresponding observations for the winter experiments and 40 W m−2 for the June experiment. Differences in net long-wave radiation fluxes range from −5 to 12W m−2 in winter and −62W m−2 for the June experiment. The correspondence between measured and calculated momentum fluxes is very high, which confirms the usability of our model component for calculating surface winds and wind stresses from the atmospheric surface pressure.