Barotropic aspects of the dynamics of the Gulf of Naples (Tyrrhenian Sea)

Process-oriented studies are carried out in order to analyze barotropic dynamical features in the Gulf of Naples: gravitational normal mode oscillations (seiches) of the gulf and depth-averaged circulations induced directly by the wind and remotely by the large-scale Tyrrhenian circulation. The shallow water equations are solved numerically in a domain which includes the Gulf of Naples and an external buffer zone whose role is two fold: it is required to remove the effect of a fictitious boundary in the determination of the seiches and it allows the imposition of boundary conditions related to the large-scale circulation in the Tyrrhenian Sea, which contributes to determine the internal circulation via topographic coupling. The seiches are studied by means of a spectroscopic analysis in which eigenoscillations are generated by the relaxation of a wind setup. The eigenperiods corresponding to the main seiches are determined and the corresponding horizontal spatial structures are presented. Good agreement is found when comparing these numerical modelling results with tide gauge records. The wind and boundary-driven depth-averaged circulation in the gulf is then studied by imposing idealized local winds and external currents chosen on the basis of realistic modelling of the wind-driven circulation of the Tyrrhenian Sea. Both quasi-steady and typical transient-time dependence are taken into account, so that a series of circulation schemes is obtained representing typical dynamic scenarios in the Gulf of Naples. The results are related to the observations and good agreement is found.