Description: A primitive equation model to study the dynamics of the Agulhas system has been developed. The model domain covers the South Atlantic and the south Indian Ocean with a resolution of ⅓° in the Agulhas region while coarser outside. It is driven by a climatology of the European Centre for Medium-Range Weather Forecasts. It is shown that the model simulates the Agulhas Current, its retroflection, and the ring shedding successfully. The model results show baroclinic anticyclonic eddies in the Mozambique Channel and east of Madagascar, which travel toward the northern Agulhas Current. After the eddies reach the current they are advected southward with the mean flow. Due to the limited numerical resolution only a few eddies reach the retroflection region without much modification. These eddies are responsible for drastic enhancement of the heat transfer from the Indian Ocean to the South Atlantic and lead to periodicities in the interoceanic heat transport of about 50 days superimposed on the seasonal variability. Combined satellite data from TOPEX/Poseidon and ERS-1 show that the observed vortices in the Mozambique Channel are comparable to those seen in the model. In contrast to this the simulated eddies east of Madagascar seem not to be well reproduced. Analyses of the energy conversion terms between the mean flow and the eddies suggest that barotropic instability plays an important role in the generation of Mozambique Channel eddies. For the generation of Agulhas rings and other eddy structures in the model the barotropic instability mechanism seems to be minor, and baroclinic instability mechanisms are more likely.

Description: If only the periode of internal waves is governed by tide generating force the wave length is a free parameter. Then in a two-layered ocean (horicontal unbounded) internal waves with large amplitude and with the same periode as tide generating force are possible. The wave length of these waves corresponds to the case of resonance which follows from theory of free waves.

Description: Mit Hilfe des Verfahrens von J. W. TUKEY werden gefilterte und ungefilterte Energie- bzw. Amplitudenspektren der Wasserstandsschwankungen des Jahres 1958 an 31 Pegelstationen entlang der Ostseeküste berechnet (Durchlaßbereich des Filters 6h-50h). Für benachbarte Stationen werden ferner Co- uncl Quadratur-Spektren sowie Phasendifferenz und Kohärenz berechnet. Aus den Spektren der gefilterten Meßreihen wird die Verteilung der Amplituden der S2-, M2-, K1- und O1-Tide ermittelt. Dabei wird unterschieden zwischen den Amplituden, die der Gesamtenergie im Spektrum bei den Gezeitenperioden entsprechen und denjenigen, die aus der Energiedifferenz zwischen der Gesamtenergie und der mittleren Energie des meteorologisch bedingten Spektralniveaus resultieren. Die ungefilterten Spektren zeigen mit Ausnahme der Stationen des Finnischen Meerbusens eine Energiekonzentration im Bereich von etwa 120h. Es wird eine spezielle Situation gefunden, in der die Wasserstände weitgehend durch eine 120-stündige Periodizität beschrieben werden können. Diese Periodizität erweist sich als stehende, winderzeugte Welle. Energy and amplitude spectra with and without a bandpass filter from 6h-50h of the 1958 sea level records from 31 tide gauges along the coast of the Baltic have been computed by means of the method of J. W. TUKEY. For neighbouring stations co- and quadrature-spectra, phase difference and coherence have also been computed. The amplitude and phase distribution of the S2, M2, K1 and 01 tide have been derived from the filtered spectra. The amplitudes corresponding to the total energy at the tidal periods and those resulting from the energy difference between the total energy and the noise energy are given separately. The spectra computed without filtering show an energy concentration in the range of about 120h except at the stations of the Gulf of Finland. A special situation has been found where the water level can be described by a 120h periodicity to a large extent. This periodicity turns out to be a standing wave forced by wind.