Articles | Volume 18, issue 14
https://doi.org/10.5194/gmd-18-4685-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gmd-18-4685-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Model description paper
| 
30 Jul 2025
Model description paper |
| 30 Jul 2025
| 30 Jul 2025
Comparing an idealized deterministic–stochastic model (SUP model, version 1) of the tide- and wind-driven sea surface currents in the Gulf of Trieste to high-frequency radar observations
Sofia Flora
CORRESPONDING AUTHOR
Department of Mathematics, Informatics and Geosciences, University of Trieste, Trieste, Italy
National Institute of Oceanography and Applied Geophysics – OGS, Trieste, Italy
Laura Ursella
National Institute of Oceanography and Applied Geophysics – OGS, Trieste, Italy
Achim Wirth
Univ. Grenoble Alpes, CNRS, Grenoble INP, LEGI, 38000 Grenoble, France
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This study analyses the extreme meteo-marine event October–November 2023 in the Gulf of Trieste, characterised by southerly strong winds, heavy rainfall, and high river discharge. Using HF radar data, wind records, and numerical models, we analysed the interactions between river discharge and wind-driven currents. Results show that strong river discharge can dominate coastal circulation and overlay the wind effects. This multi-platform approach provides valuable insights into ocean dynamics.
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An increasing amount of data allows us to move from low-order moments of fluctuating observations to their PDFs. We found the analytical fat-tailed PDF form (a combination of Gaussian and two-exponential convolutions) for 2 years of sea surface current increments in the Gulf of Trieste, using superstatistics and the maximum-entropy principle twice: on short and longer timescales. The data from different wind regimes follow the same analytical PDF, pointing towards a universal behaviour.
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The hydrostatic approximation is the basis of most simulations of ocean and climate dynamics. It is evaluated here by using a projection method in the 4D Fourier space. The evaluation is analytic.
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This study analyses the extreme meteo-marine event October–November 2023 in the Gulf of Trieste, characterised by southerly strong winds, heavy rainfall, and high river discharge. Using HF radar data, wind records, and numerical models, we analysed the interactions between river discharge and wind-driven currents. Results show that strong river discharge can dominate coastal circulation and overlay the wind effects. This multi-platform approach provides valuable insights into ocean dynamics.
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Analysis of a high-frequency time series of thermohaline data measured at the EMSO-E2M3A regional facility in the southern Adriatic Pit (SAP) reveals a significant change in the double-diffusive regime in 2017 associated with the intrusion of extremely salty waters into the area, suggesting salt fingering as the dominant regime. The strong heat loss at the surface during this winter allowed deep convection to transport this high-salinity water from the intermediate to deep layers of the pit.
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An increasing amount of data allows us to move from low-order moments of fluctuating observations to their PDFs. We found the analytical fat-tailed PDF form (a combination of Gaussian and two-exponential convolutions) for 2 years of sea surface current increments in the Gulf of Trieste, using superstatistics and the maximum-entropy principle twice: on short and longer timescales. The data from different wind regimes follow the same analytical PDF, pointing towards a universal behaviour.
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Explaining the dynamics of jellyfish blooms is a challenge for scientists. Biological and meteo-oceanographic data were combined on different timescales to explain the exceptional bloom of the jellyfish Rhizostoma pulmo in the Gulf of Trieste (Adriatic Sea) in April 2021. The bloom was associated with anomalously warm seasonal sea conditions. Then, a strong bora wind event enhanced upwelling and mixing of the water column, causing jellyfish to rise to the surface and accumulate along the coast.
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High-frequency radar (HFR) is a land-based remote sensing technology that can provide maps of the surface circulation over broad coastal areas, along with wave and wind information. The main goal of this work is to showcase the current status of the Mediterranean HFR network as well as present and future applications of this sensor for societal benefit such as search and rescue operations, safe vessel navigation, tracking of marine pollutants, and the monitoring of extreme events.
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In non-equilibrium statistical mechanics, which describes forced-dissipative systems such as air–sea interaction, there is no universal probability density function (pdf). Some such systems have recently been demonstrated to exhibit a symmetry called a fluctuation theorem (FT), which strongly constrains the shape of the pdf. Using satellite data, the mechanical power input to the ocean by air–sea interaction following or not a FT is questioned. A FT is found to apply over specific ocean regions.
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Experiments in rotating tanks can simulate the Earth system and help to represent the real ocean, where rotation plays an important role. We wanted to show the minor importance of the wind in driving the flow in the Ionian Sea. We did this by observing changes in the water current in a rotating tank affected only by the pumping of dense water into the system. The flow variations were similar to those in the real sea, confirming the scarce importance of the wind for the flow in the Ionian Sea.
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We show that modern concepts of non-equilibrium statistical mechanics can be applied to large-scale environmental fluid dynamics, where fluctuations are not thermal but come from turbulence. The work theorems developed by Jarzynski and Crooks are applied to air–sea interaction. Rather than looking at the average values of thermodynamic variables, their probability density functions are considered, which allows us to replace the inequalities of equilibrium statistical mechanics with equalities.
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Short summary
We developed a hierarchy of idealized deterministic–stochastic models to simulate sea surface currents in the Gulf of Trieste. They include tide- and wind-driven sea surface current components, resolving the slowly varying part of the flow, and a stochastic signal, representing the fast-varying small-scale dynamics. The comparison with high-frequency radar observations shows that the non-Gaussian stochastic model captures key dynamics and mimics the observed fat-tailed probability distribution.
We developed a hierarchy of idealized deterministic–stochastic models to simulate sea surface...
