ROSSBY RADII AND PHASE SPEEDS IN THE BALTIC SEA

On the basis of a data set recorded during seasonal cruises of the R.V.s A.v. Humboldt and Prof. A. Penck of the Academy of Sciences, G.D.R., in the Baltic Sea during 1977-1987, mean Brunt-Vaisala frequency profiles were derived in order to compute vertical eigenvalues and internal, or baroclinic, Rossby radii for different seasons in various parts of the Baltic Sea. Due to regional variations of stratification and the depth of the different basins, these parameters vary considerably. Moreover, the Rossby radii show a seasonal cycle with minimum values during the winter and autumn, and maxima during summer. The largest Rossby radius, 7 km, was found in the Bornholm Basin and the smallest ones, 1.3 km, in the Belt Sea and in the Gulf of Finland during autumn. Approximated Rossby radii, as obtained by a WKB treatment, appear to be too small by about 10-30%.