ASTRONOMICAL TIDE HEIGHT ALONG ITALIAN COASTS

Panel 1

Data aggiornamento scheda

2024-12-31

Autori

Andrea Bianco, Saverio Devoti, Sara Morucci, Gabriele Nardone, Luca Parlagreco, Marco Picone, Giulio Settanta

Abstract

The tide is a periodic phenomenon of rising and falling sea levels caused by the gravitational attraction exerted by the Moon, the Sun, and other celestial bodies on the Earth's water masses, and secondarily by meteorological disturbances. Data from the National Tide Gauge Network (ISPRA) were used to characterize the amplitude of the astronomical component of the tidal signal along Italian coasts. As well known, astronomical tides vary significantly across the different Italian seas, reaching their maximum range in the Northern Adriatic and Venice Lagoon, being strongly influenced by the basin's configuration.

Descrizione

The tidal phenomenon involves the rising and lowering of sea levels due to the gravitational pull mainly exerted by the Moon and the Sun on the Earth's surface, and secondarily by meteorological phenomena. Two components can thus be distinguished: an astronomical, periodic, and predictable component, and a stochastic, meteorological component. The rising phase reaches its peak during the maximum elevation of sea levels, referred to as high tide (or crest), while the lowest phase is called low tide (or trough). The difference between high and low tide is known as tidal range or amplitude. Tidal ranges vary over time based on the relative positions of the Earth-Sun-Moon system and spatially according to morphological features such as sea floor depth, coast shape, and water mass area. Sea levels are recorded along Italian coasts by tide gauge stations, primarily located within ports and managed by ISPRA. Astronomical tides were calculated using 69 harmonic constants that account for periodicities strictly linked to astronomical phenomena and those induced by meteorological phenomena. As indicated in literature, for practical modeling applications, especially in the Northern Adriatic and Venice Lagoon, where the phenomenon is most intense, only the seven main harmonic constants may be used. Conversely, for purely knowledge-related purposes and scientific research, utilizing 69 harmonic constants across the Mediterranean is recommended.

Scopo

Monitoring and characterizing the astronomical tide component along Italian coasts can be particularly useful for identifying anomalies and extreme tidal phenomena relative to the natural condition of the sea, which varies at each measurement point.

Rilevanza

È di portata nazionale oppure applicabile a temi ambientali a livello regionale ma di significato nazionale

È semplice, facile da interpretare.

Fornisce un quadro rappresentativo delle condizioni ambientali, delle pressioni sull'ambiente e delle risposte della società.

Fornisce una base per confronti internazionali.

Solidità

È basato su standard nazionali/internazionali e sul consenso nazionale/internazionale circa la sua validità

È ben fondato sul piano tecnico e scientifico.

Presenta affidabilità e attendibilità dei metodi di misurazione e raccolta dei dati

Comparabilità nel tempo

Comparabilità nello spazio

Misurabilità (dati)

Adeguatamente documentati e di fonte nota

Aggiornati a intervalli regolari e con procedure affidabili

Facilmente disponibili o resi disponibili a fronte di un ragionevole rapporto costi/benefici

Un’ “adeguata” copertura spaziale

Un’ “idonea” copertura temporale

Principali riferimenti normativi e obiettivi

Addresses knowledge requirements established in Directive 2000/60/EC regarding coastal and transitional waters, and Directive 2007/60/EC regarding coastal floods and inundations. No specific objectives are defined by legislation.

Panel 2

DPSIR

Stato

Tipologia indicatore

Descrittivo (A)

Riferimenti bibliografici

https://dati.isprambiente.it/dataset/rmn/

https://www.mareografico.it/

Data quality assessment

Fonte dei dati

ISPRA

Frequenza di rilevazione dei dati

Annuale

Continuos

Accessibilità dei dati di base

http://dati.isprambiente.it/dataset/rmn-la-rete-mareografica-nazionale/

Copertura spaziale

Italian seas

Copertura temporale

1971 - 2023

Indicator assessment

Core SET

EEA - Set of Indicators

Descrizione della metodologia di elaborazione

Tides in the Mediterranean Sea have a frequency of approximately 12 hours, related to the passage of the Moon above an observation point on Earth. Thus, tides are influenced differently throughout the month depending on lunar phases. This component, known as astronomical tide, is reconstructed and presented. The measured signal, with its harmonic component subtracted, provides residuals containing information on stochastic meteorological phenomena that occurred.

Periodicità di aggiornamento

Annuale

Data quality

The astronomical tide is an excellent indicator for characterizing normal oscillations in sea levels, enabling geographic comparisons on a national scale and monitoring variations induced by short- or long-term physical phenomena over time. Data are acquired from tide gauge stations of the National Tide Gauge Network (RMN), ensuring spatial coverage across the entire country, hourly sampling, and multi-year historical series. Sea level data have undergone a validation process manually executed by expert judgment, classified as L2 according to WMO standards, and analyzed using the most accredited and advanced statistical methods. Specifically, 69 harmonic constants were used for reconstructing the astronomical tide signal. This indicator thus provides an excellent basis for national-scale comparison.

Stato

Non definibile

Trend

Non definibile

Valutazione/descrizione dello stato

This indicator is defined based on universal constants describing a phenomenon without characterizing any specific state.

Valutazione/descrizione del trend

This indicator is defined based on universal constants, which are not expected to change over time and therefore do not highlight any trend. Possible oscillations and differences over the years are attributed to purely stochastic phenomena, and consequently, trend evaluation is not anticipated.

Commenti

The indicator refers to 2023 and is presented to uniformly characterize astronomical tides locally along Italian coasts, updating and aligning values relative to observed data. Analyses from the Trieste and Venice stations, as is well known, show significantly higher astronomical tide levels in the Northern Adriatic (Venice and Trieste), with maximum and minimum tides nearly three times those recorded at other measurement stations (Tyrrhenian Sea) (Table 1). This is apparent in Figures 14, 15, 16, and 17 for both Venice and Trieste stations; Figures 14 and 16 depict the astronomical tide trend on the same scale as other Italian stations to highlight the phenomenon's intensity (and its exceeding the scale), while Figures 15 and 17 represent the astronomical tide in its entirety on the appropriate scale. The intense tidal effect in the Venice Lagoon is well recognized and reflected in this indicator's data. The nearly 50-year time series (1971–2023) allow detailed study of any oscillations in the astronomical tide components, predominantly due to stochastic phenomena, and monitoring their substantial stability over time, as expected from the governing physical phenomenon. Additionally, the availability of data distributed along all Italian coasts enables precise evaluation of the astronomical phenomenon, of extraordinary interest and utility even in operational forecasting contexts.

Data

Allegati