ASTRONOMICAL TIDE HEIGHT ALONG ITALIAN COASTS

    Descrizione 1
    Update date
    Authors

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

    Abstract
    Immagine
    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.

    Description

    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.

    Purpose

    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.

    Policy relevance and utility for users
    It is of national scope or it is applicable to environmental issues at the regional level but of national relevance.
    It is simple and easy to interpret.
    It provides a representative picture of environmental conditions, environmental pressures, and societal responses
    It provides a basis for international comparisons.
    Analytical soundness
    Be based on international standards and international consensus about its validity;
    Be theoretically well founded in technical and scientific terms
    Presents reliability and validity of measurement and data collection methods
    Temporal comparability
    Spatial comparability
    Measurability (data)
    Adequately documented and of known quality
    Updated at regular intervals in accordance with reliable procedures
    Readily available or made available at a reasonable cost/benefit ratio
    An “adequate” spatial coverage
    An “appropriate” temporal coverage
    Main regulatory references and objectives

    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.

    DPSIR
    State
    Indicator type
    Descriptive (A)
    Frequenza di rilevazione dei dati
    Annuale
    Continua
    Fonte dei dati
    ISPRA
    Data availabilty

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

    Spatial coverage

    Italian seas

    Time coverage

    1971 - 2023

    Processing methodology

    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.

    Update frequency
    Year
    Qualità dell'informazione

    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.

    State
    Undefinable
    Trend
    Undefinable
    State assessment/description

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

    Trend assessment/description

    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.

    Comments

    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
    Thumbnail
    Headline

    Figura 1: Mare astronomica stazione Ancona (2022)

    Data source

    ISPRA -  RMN

    Thumbnail
    Headline

    Figura 2: Marea astronomica statione Anzio (2023)

    Data source

    ISPRA - Rete nazionale di Mareografica (RMN)

    Thumbnail
    Headline

    Figura 3: Marea astronomica statione Carloforte (2023)

    Data source

    ISPRA - Rete mareografica nazionale (RMN)

    Thumbnail
    Headline

    Figura 4: Marea astronomica statione Catania (2023)

    Data source

    ISPRA - RMN

    Thumbnail
    Headline

    Figura 5: Marea astronomica stazione Civitavecchia (2023)

    Data source

    ISPRA - RMN

    Thumbnail
    Headline

    Figura 6: Marea astronomica statione Gaeta (2023)

    Data source

    ISPRA - RMN

    Thumbnail
    Headline

    Figura 7: Marea astronomica statione Imperia (2023)

    Data source

    ISPRA - RMN

    Thumbnail
    Headline

    Figure 8: Astronomical tide station Lampedusa (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 9: Astronomical tide station Livorno (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 10: Astronomical tide Otranto station (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 11: Astronomical tide Porto Torres station (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 12: Astronomical tide station Ravenna (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 13: Astronomical tide station San Benedetto del Tronto (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 14: Astronomical tide station Trieste (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 16: Astronomical tide station Venezia (2023)

    Data source

    SPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 18: Astronomical tide station Vieste (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 15: Astronomical tide station Trieste - zoom (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Thumbnail
    Headline

    Figure 17: Astronomical tide Venice station - zoom (2023)

    Data source

    ISPRA - National Mareographic Network (RMN)

    Headline

    Table 1: Values of the astronomical tide along the Italian coasts

    Data source

    ISPRA - RMN

    English