Observing Meteorological Tides: Fifteen Years of Statistics in the Port of La Spezia (Italy)

Abstract

Sea level changes in coastal areas significantly influence port activities (e.g., the safety of navigation). Along Italian coastlines, sea level variations are mainly due to astronomical tides (well known, due to gravitational attraction between Earth, Moon and Sun); however, during the last fifteen years, a high number of “anomalous” tides has been observed: the study of the phenomenon has allowed to attribute its cause to variations in atmospheric pressure (the so-called meteorological tides: sea level drops when atmospheric pressure increases and vice versa); the statistical analysis of acquired data made it possible to evaluate the hydrobarometric transfer factor (a local parameter which represents the correlation between atmospheric pressure changes and consequent sea level variations): it was found that it is usually much larger within gulfs or port basins than offshore areas, where a pressure change of 1 hPa results in a sea level variation of about 1 cm; the statistical analysis described in the following, and aimed at correctly estimating the hydrobarometric transfer factor in harbors, can play a fundamental role in optimizing the management of port waters: its results allow to forecast meteorological tides and therefore future sea level (and depth) variations in a given port basin. The results of the study conducted in the port of La Spezia (North Western Italy) are presented here, together with possible applications on port activities and harbor water management.