The comparison of the forecasted and measured currents in the deep part of the Southern Baltic Sea in 1999

This paper presents results of the investigation carried out in frame of research project of Institute of Meteorology and Water Management Maritime Branch in Gdynia (IWM-MB) in the y ear 2000. The goal of the project was to determine the conformity of the sea current forecasts for the layer 8 - I 2 meters of the open sea part of the Southern Baltic Sea, as produced by the hydrodynamic model of the Baltic Sea- HIROMB [5}, with the measurements. Contrary to the results of previous experiments as in the case of the POLRODEX ones [7, 8, 9}, during present study it was expected to detect behaviour of the model far from the influence of the boundary like coastline as well as bottom friction in the shallow water areas. The analysed data were collected during five routine cruises of r/v Baltica organized by IWMMBsince February until September I999 [10], when cruise track started/rom the Gdansk Deep, next along the northern border of the Polish EEZ, ending in the Bomholm Deep area usually. On the basis of the current vectors recorded by means of the ship mounted ADCP as the 250 m average values in the layer 7.5 to 12.5 meters, mean values related to the model grid have been calculated and statistically assessed. These mean vectors have been used for compan·son of forecasted values. Consequently, the sets of values of the differences between measured and predicted currents were statistically evaluated both regarding the direction and the module of the currents as well as the current vector components (Vx, Vy) separately.