Percorrer por autor "Lopez-Ruiz, A."
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- Diagnosis of residual flow drivers in estuaries with the densimetric tidal Froude numberPublication . Khosravi, Maziar; Fortunato, A. B.; Lopez-Ruiz, A.; Valle-Levinson, A.; Garel, ErwanResidual circulation in estuaries drives salt intrusion, material transport, and ecosystem functioning. Yet the ability to diagnose its dominant forcing mechanism remains a challenge. While previous studies suggest that the densimetric tidal Froude number () may distinguish tidal from baroclinic forcing, its reliability across varying estuarine conditions and spatial scales requires systematic evaluation. This study carries out such evaluation with a suite of process-oriented numerical simulations in an idealized estuary–shelf system that features Gaussian cross-channel bathymetry. Here, is treated as a diagnostic indicator reflecting the dynamics established by either barotropic or baroclinic forcing. The model configuration spans a parameter space that includes variations in tidal amplitude, channel depth, lateral slope, and river discharge. Residual circulation regimes are diagnosed using the ratio between the barotropic and baroclinic terms of the tidally averaged, axial momentum equation obtained from model outputs. Diagnoses are made together with the transverse structure of residual flows, allowing direct comparison with predictions. This study demonstrates that can reliably diagnose the dominant driver of residual circulation when the density length scale is defined over the shortest feasible axial distances. Crucially, the results show that the skill of is highly sensitive to this spatial scale: its performance deteriorates when the density gradient is computed over lengths that extend into regions with heterogeneous forcing. Across all simulations, functions as a robust bulk indicator of tide-dominated, density-dominated, or regimes influenced by both forcings only when the density scale is restricted to zones where the axial density gradient is approximately constant. Such zones consistently occupy the seaward side of the peak salinity gradient. Within this region, emerges as a relevant diagnostic tool and offers process-oriented guidance for results that require identifying the prevailing residual-flow driver. The experiments suggest configuration-dependent ranges associated with regimes dominated by tides, density gradients, or both
- Fortnightly variability of the lateral structure of residual flows along non-rotating estuariesPublication . Khosravi, Maziar; Fortunato, A. B.; Lopez-Ruiz, A.; Valle-Levinson, A.; Garel, ErwanResidual circulation in estuaries plays a crucial role in controlling salt intrusion, material transport, and ecosystem functioning, making its understanding essential for coastal management worldwide. Despite its importance, the mechanisms driving the transverse structure of residual flows remain insufficiently explored, particularly in relation to the fortnightly tidal variability. This study shows how the main driver of residual flow may switch from baroclinic dominance at neap tide to barotropic dominance at spring tide. Three-dimensional, process-oriented numerical simulations are carried out in an idealized, non-rotating, estuary–shelf system, represented by an 80 km-long semi-closed channel with a 1 km-wide Gaussian-shaped cross-section. This setting is inspired by the Guadiana Estuary (Portugal/Spain), where previous observations have reported a switch of the residual circulation between spring tide and neap tide. To mimic such fortnightly pattern, the model is forced by freshwater inflow at the head and M2 and S2 tidal harmonics at the ocean boundary. Harmonic amplitudes were selected based on a sensitivity analysis. The along channel and temporal variability of the lateral structure of axial residual flows is represented using a non-dimensional parameter derived from the residual inflow that may develop in the deep channel. The simulation results show residual flow transverse structures consistent with theoretical expectations for a baroclinic driver in neap tides and a barotropic driver in spring tides, as confirmed by analyses of the residual momentum equation terms. In these cases, the near-bottom residual flow in the channel is relatively strong and its direction indicates the dominant driver. The study also reveals a previously undocumented transverse structure described by inflows near the channel bed and over the shoals. This structure develops in relation to the Stokes drift when baroclinic and barotropic forcings are relatively balanced across a section.