Application of a sigma-coordinate baroclinic model to the Baltic Sea

A three-dimensional (3-D) sigma-coordinate baroclinic model is used to investigate water circulation and thermohaline variability in the Baltic Sea. Two versions of the horizontal resolution of ~ 10 km and ~ 5 km with 24 sigma-levels in the vertical are considered. The model is based on the Princeton Ocean Model code of Blumberg & Mellor (1987) and Mellor (1993), known as POM. This paper presents details of simulation strategies and briefly discusses the 'reality' of the results of modelling. The model's capabilities of simulating the characteristic hydrographic features of the Baltic Sea were tested for 3 months (August-October 1995), a simulation related to the period of the PIDCAP'95 experiment (Pilot Study for Intensive Data Collection and Analysis and Precipitation) (Isemer 1996). The model results are compared with the in situ measurements of temperature and salinity at selected hydrographic stations, collected during cruises of r/v 'Oceania' in September and October 1995. Comparison of computed and measured temperature and salinity shows that the model reproduces the vertical structure of seawater temperature and salinity in relatively good accordance with the in situ observations. The differences between the calculated and observed values of temperature and salinity are c. 1-2oC and c. 1-2 PSU, depending on the location of the hydrographic station.