# Observing Meteorological Tides: Fifteen Years of Statistics in the Port of La Spezia (Italy)
## 5 Conclusions  
In Mediterranean harbors, tides are mainly due to astronomical and meteorological components; while the first ones are well known and predictable everywhere by means of a deterministic law (tide charts), the second ones (due to atmospheric disturbances) need more study: starting from monitoring environmental parameters in La Spezia harbor (Ligurian Sea, North-Western Italy), we performed a statistical analysis over the last fifteen years (starting from the installation of ISPRA's monitoring station in 2006) to evaluate the hydrobarometric transfer factor, which represents the correlation between atmospheric pressure (cause) and sea level variations (effect) and therefore can play a fundamental role in forecasting meteorological tides in harbors. We found that the hydrobarometric transfer factor in La Spezia harbor is larger (sometimes more than double) than in offshore areas (where 1 hPa of atmospheric pressure gradient induces nearly 1 cm of sea level rise/fall); thus, some hPa of atmospheric gradient can induce several cm of sea level rise/fall. In particular, we found that using \(J_{ph}\) = 1.9 cm \(*\) hPa\({}^{-1}\) results in an estimate of the average error of about 11.3%, while approximating the dependence of sea level on atmospheric pressure by means of a nonlinear (cubic) law reduces the mean error to about 9.6%. This error very rarely induces confusion between different colors along the edges of adjacent areas in the map representing virtual traffic lights described above. Furthermore, meteorological tides can cause exceptional changes in sea level if they occur in conjunction with astronomical components: the observation of the phenomenon allowed us to highlight anomalous\" tides, sea level changes that are very different from the expected astronomical tides. The hydrobarometric transfer factor allows to forecast meteorological tides in the sea basin examined and then, simply by adding the contribution of the astronomical tides, to know in advance the sea level (and therefore water depth) expected in the near future; this can represent a useful tool for optimizing port activities and logistic operations by planning them in advance. Since sea level changes in coastal areas affect in a relevant way the safety of port communities, a prototype application has been developed that updates the port bathymetric map based on sea level acquired in real time or forecasted, with the aim of planning and optimizing port activities or managing emergencies (it is also able to load old measurements stored in a dataset, e.g., to analyze accidents occurred in the past); the software tool classifies the port bathymetric map in forbidden (red), warning (yellow), or permitted (green) areas for a certain ship at a given moment, based on its draught (virtual traffic lights); the graphical interface is able to detect and easily signal hazardous situations in harbors in order to provide a useful support to decision makers (port authorities, coast guards), with the aim of increasing safety for people working in ports. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app122312202/s1](https://www.mdpi.com/article/10.3390/app122312202/s1)]([https://www.mdpi.com/article/10.3390/app122312202/s1](https://www.mdpi.com/article/10.3390/app122312202/s1)), Figure S1. Measurements carried out between 21 and 27 February 2007 inside the port of La Spezia: (**a**) atmospheric pressure; (**b**) sea level (\(\Delta\)p = 10 hPa, \(\Delta\)h = 16 cm, \(J_{ph}\) = 1.6 cm \(*\) hPa\({}^{-1}\)). Figure S2. Measurements carried out between 25 February and 1 March 2007 inside the port of La Spezia: (**a**) atmospheric pressure; (**b**) sea level (\(\Delta\)p = 9.8 hPa, \(\Delta\)h = 16.4 cm, \(J_{ph}\) = 1.7 cm \(*\) hPa\({}^{-1}\)). Figure S3. Measurements carried out between 9 and 16 May 2007 inside the port of La Spezia: (**a**) atmospheric pressure; (**b**) sea level (\(\Delta\)p = 5.9 hPa, \(\Delta\)h = 16.1 cm, \(J_{ph}\) = 2.7 cm \(*\) hPa\({}^{-1}\)). Figure S4.