Prevailing patterns of the sound speed distributions in the environment of the Southern Baltic

The paper contains the results of experimental and
theoretical research aimed at elaborating characteristic features of the
acoustic conditions in the Southern Baltic. As there features are fully
dependent on the hydrological conditions, the sound speed distribution is
influenced by many factors and changes during the year. On the basis of
hydrological data recorded from 1979 to 1991 by measurements at stations
situated along the deeps of the Southern Baltic, the sound speed has been
calculated using the procedure of Chen Millero recommended by UNESCO. The data
were averaged in one-months periods and subjected to a detailed analysis of the
speed vibrations during the year. The patterns of the sound speed distribution
characteristic for every month have been determined. Research was also conducted
to find to what extent the synoptic patterns of the sound speed distribution
differ from the averaged respective data. To solve the problem, several synoptic
distributions established in different seasons are compared with the averaged
distribution. Difficulties in specifying the acoustical conditions of the
Southern Baltic are augmented by the appearance of short-term local phenomena
changing considerably the sound speed distribution in certain areas. Examples of
such phenomena are presented in the paper. The paper is based on a large number
of in situ measurement data presented in the form of diagrams.