J.Sennikovs, U.Bethers, Laboratory for Mathematical Modelling of Environmental and Technological Processes, University of Latvia.
 

The Gulf of Riga is a well-defined semi enclosed water basin of average depth  25.5m connected with the Baltic Proper by two straits.
The formulation of the shallow water model for the Gulf of Riga has been given together with the physical situation analysis. Conditions of applicability of such a model without accounting for the density stratification have been investigated. Model can be applied for qualitative investigations of the reaction of the Gulf to meteorological forcing, obtaining the typical flow and surface elevation patterns. It is suitable also  for real-time calculations in the autumn-winter periods. Calculations for characteristic flow patterns as well as for characteristic transient situations and real time periods have been performed. The results have been compared with the water level observations. The comparison has shown reasonable agreement between model predictions and observations for the autumn periods with negligible stratification. The real time calculations indicate absence of permanent wind-driven currents in the Gulf of Riga caused by rather strong variability of meteorological forcing. Calculations show that structure of interchanging cyclonic/anticyclonic vortexes weakens water exchange between northern and southern parts of the Gulf and, as a consequence, between the Gulf and the Baltic Proper.