Modeling of Co-Oscillating and Direct Tides

The tidal analysis of this study was based on archived data of prediction runs on the BSH s operational model system (Dick et al., 2001). As has been pointed out above, these studies only made sense because the model had been trained for independent tides (Muller-Navarra 2002), and it has been shown that by incorporating this improvement it has been possible to compute much more realistic water levels, at least with respect to strictly periodic water level flucmations (Miiller-Navarra and Lange, 2004). Otherwise important tidal constituents would be missing in the Baltic water-level time series, especially those in the Baltic Proper, Bay of Bothnia, and Gulfs of Finland and Bothnia. It is possible to extract time series for all grid points from the BSH s model archive and carry out a harmonic analysis in exactly the same way as with measured time series. 

For each grid point in the Baltic Sea and Kattegat, time series of 369 x 24 -F 1 = 8857 hourly values of water levels in the period from 1.1.2005 1 00 UTC to 5.1.2006 0 (X) UTC were compiled and analyzed harmonically. By choosing this long time series of well over 1 year, it has been made sure that aU essential tidal constituents were recorded individually the differences between the angular velocities are all greater than 360°/8856 h 0.04065°/h. 

With the model approach described above, it has been possible, for the first time, to represent the tides in the entire B altic Sea, which could not be done using the measured water level data from coastal gauge stations. 

To characterize the tidal conditions in a particular sea, it is sufficient to select the four major tidal constituents in terms of their theoretical importance, two semidiurnal and two diurnal ones (M2, S2, Kj, Oj). 

The quotient of the amplimdes of the four tidal constituents / (Oi + Ki)/(M2 4- S2) then yields the form number, indicating whether the tides rather are of the diurnal or semidiurnal type, and the sum the four amplitudes I = Oi + Ki + M2 + S2 is the intensity. 

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