WIT Press

A Model For Storm Surge Forecasts In The Eastern Baltic Sea


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Ü. Suursaar, T. Kullas, M. Otsmann & T. Kõuts


Historical data are statistically analysed and sea levels are dynamically modelled in the coastal areas of Estonia. The 2D model is used for the description of both typical sea level developments and extreme events. The wind stress (calculated either from single-point meteorological data or from HIRLAM wind fields) and the sea level data in the open boundary serve as inputs. Additional calculations based on the idealistic input data are carried out for simulating storm surge and sea level resonance effects both in the Gulf of Riga and in the Neva Bay. A possible increase in the risks in the future is discussed in relation to the climate change. The simulations based on the realistic input and verification data from 1999 showed that it is possible to reproduce sea levels in the study area and develop an operational system for predicting extreme sea level situations. Extreme low level events in the Gulf of Riga could reach about 130 cm below the average, they are associated with continuous eastern winds above the Baltic Sea and have little local character. The high levels (up to 280 cm) are associated with SW and W storms. They appear, firstly, due to the water volume change in the Baltic Sea, secondly, due to the additional volume increase in the Gulf, and finally, due to the local level slope and long wave effect in some suitably narrow and shallow bays of the Gulf. An amplification due to resonance is possible. 1 Introduction Storm surges occasionally appearing in the Eastern Baltic Sea (Fig.1), can pose serious risks for nearshore inhabitants. Frequent passages of atmospheric pressure systems generate strong winds and considerable water level fluctuations. The highest extremes of the Baltic Sea level could be found in the SW (Kiel, Schleswig, +316 cm) and in the NE (Neva Bay, +423 cm) [1,2]. The