Preprints
https://doi.org/10.5194/egusphere-2024-3391
https://doi.org/10.5194/egusphere-2024-3391
16 Jan 2025
 | 16 Jan 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 HF Radar observations

Sofia Flora, Laura Ursella, and Achim Wirth

Abstract. In the Gulf of Trieste the sea surface currents are observed by High Frequency Radar for almost two years (2021–2022) at a temporal resolution of 30 min. We developed a hierarchy of idealized models to simulate the observed sea surface currents, combining a deterministic and a stochastic approach, in order to reproduce the externally forced motion and the internal variability, which is characterized by a fat-tailed statistics. The deterministic signal includes tidal and Ekman forcing and resolves the slowly varying part of the flow, while the stochastic signal represents the fast-varying small-scale dynamics, characterized by Gaussian or fat-tailed statistics, depending on the statistical used. This is done using Langevin equations and modified Langevin equations with a Gamma distributed variance parameter. The models were adapted to resolve the dynamics under nine tidal and wind Forcing Protocols in order to best fit the observed forced motion and internal variability Probability Density Function (PDF). The stochastic signal requires 2 stochastic degrees of freedom when the averaged tidal forcing is adopted, while it needs 1/2 stochastic degree of freedom when the complete tidal forcing is used. Despite its idealization, the deterministic-stochastic model with stochastic fat-tailed statistics captures the essential dynamics and permits to mimic the observed PDF. Moreover, a Fluctuation Response Relation is valid when the stochastic signal is perturbed, showing that the response to an external perturbation can be obtained by considering the fluctuations of the unperturbed system.

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Journal article(s) based on this preprint

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, Laura Ursella, and Achim Wirth
Geosci. Model Dev., 18, 4685–4712, https://doi.org/10.5194/gmd-18-4685-2025,https://doi.org/10.5194/gmd-18-4685-2025, 2025
Short summary
Sofia Flora, Laura Ursella, and Achim Wirth

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3391', Anonymous Referee #1, 06 Mar 2025
  • RC2: 'Comment on egusphere-2024-3391', Anonymous Referee #2, 10 Apr 2025
  • AC1: 'Comment on egusphere-2024-3391', Sofia Flora, 07 May 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3391', Anonymous Referee #1, 06 Mar 2025
  • RC2: 'Comment on egusphere-2024-3391', Anonymous Referee #2, 10 Apr 2025
  • AC1: 'Comment on egusphere-2024-3391', Sofia Flora, 07 May 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Sofia Flora on behalf of the Authors (07 May 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (12 May 2025) by Vassilios Vervatis
AR by Sofia Flora on behalf of the Authors (12 May 2025)  Author's response   Manuscript 

Post-review adjustments

AA: Author's adjustment | EA: Editor approval
AA by Sofia Flora on behalf of the Authors (29 Jul 2025)   Author's adjustment   Manuscript
EA: Adjustments approved (29 Jul 2025) by Vassilios Vervatis

Journal article(s) based on this preprint

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, Laura Ursella, and Achim Wirth
Geosci. Model Dev., 18, 4685–4712, https://doi.org/10.5194/gmd-18-4685-2025,https://doi.org/10.5194/gmd-18-4685-2025, 2025
Short summary
Sofia Flora, Laura Ursella, and Achim Wirth
Sofia Flora, Laura Ursella, and Achim Wirth

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Short summary
We developed a hierarchy of idealized deterministic-stochastic models to simulate the 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 the essential dynamics and permits to mimic the observed fat-tailed PDF.
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