A coupled wave–3-D hydrodynamics model of the Taranto Sea (Italy): amultiple-nesting approach

Abstract. The present work describes an operational strategy for the development of a multiscale modeling system, based on a multiple-nesting approach and open-source numerical models. The strategy was applied and validated for the Gulf of Taranto in southern Italy, scaling large-scale oceanographic model results to high-resolution coupled wave–3-D hydrodynamics simulations for the area of Mar Grande in the Taranto Sea. The spatial and temporal high-resolution simulations were performed using the open-source TELEMAC suite, forced by wind data from the COSMO-ME database, boundary wave spectra from the RON buoy at Crotone and results from the Southern Adriatic Northern Ionian coastal Forecasting System (SANIFS) regarding sea levels and current fields. Model validation was carried out using data collected in the Mar Grande basin from a fixed monitoring station and during an oceanographic campaign in October 2014. The overall agreement between measurements and model results in terms of waves, sea levels, surface currents, circulation patterns and vertical velocity profiles is deemed to be satisfactory, and the methodology followed in the process can constitute a useful tool for both research and operational applications in the same field and as support of decisions for management and design of infrastructures

A coupled ocean-atmosphere system for short term forecasting in the southern european seas

This coupled model combines two state-of-the-art numerical models, NEMO for the oceanic component and WRF for the atmospheric component and implements them at an appropriate resolution. The oceanic model has been implemented starting from the Mediterranean Forecasting System with a resolution of 1/24° and the domain was extended to exactly match the grid of a newly implemented atmospheric model for the same area. The uncoupled ocean model has been validated against SST observed data, both in the simulation of an extreme event and in the short-term forecast of two seasonal periods. A new setup of the model was successfully tested in which the downward radiative fluxes were prescribed from atmospheric forecasts. Various physical schemes, domain, boundary, and initial conditions were tested with the atmospheric model to obtain the best representation of medicane Ianos. The heat fluxes calculated by the uncoupled models were compared to determine which setup gave the best energy balance between the components of the coupled model. The coupling strategy used is the traditional one, where the ocean is driven by the surface stress, heat fluxes, and radiative fluxes computed in the atmospheric component, which in turn receives the SST and surface currents. As expected, the overall skills of the coupled model are slightly degraded compared to the uncoupled models, even though the positioning and timing of the cyclone at the time of the landfall is enhanced. The mean heat fluxes do not change compared to the uncoupled model, whereas the pattern of the shortwave radiation and latent heat is changed. Moreover, the two energy fluxes are larger in absolute values than those calculated with the MFS formulas. The fact that they have opposite signs give raise to a compensation error that limits the overall degradation of the coupled simulation

SHYFEM model results for the Po River-Delta-Sea system, link to NetCDF files

This dataset includes the results of the application of the SHYFEM numerical model to the Po River-Delta-Sea (RDS) system (Italy). The hydrodynamics and the interaction between riverine and marine waters in the system were studied through the application of the unstructured finite elements 3D numerical model to a domain comprising the Po river branches, 7 coastal lagoons and the shelf sea. The vertical structure of the model is z-levels, with 1 m thickness up to 10 m depth, 2 m thickness up to 26 and finally 4 m thickness to 34 m depth. The model was forced with real data of water levels, meteorological parameters and freshwater inputs. The simulations included the baroclinic gradients in the hydrodynamics calculations induced by mixing of riverine and sea waters, and by heat fluxes with the atmosphere. Two simulations were run, one for the model calibration (March - September 2009) and a two year long simulation (2010-2011) for the model validation and analysis. The SHYFEM parameter files of the two simulations are included in the data archive. The dataset includes the time-averaged hydrodynamic and T/S fields of the two simulations and of a relevant river flood in May 2009. For the 2010-2011 simulation we also provide the Water Renewal Time distribution and its range of variability. The model values calculated on the triangular finite elements grid (scalar values on the nodes and velocities on the elements) were converted into a regular grid netcdf format with horizontal spacing of 100 m. The reference coordinate system is EPSG 3003

Observational Evidence of the Basin‐Wide Gyre Reversal in the Gulf of Taranto

AbstractThe paper shows for the first time the observational evidence of basin‐wide gyre reversal in the Gulf of Taranto (north‐western Ionian Sea in the eastern Mediterranean Sea) by means of two specifically designed in situ oceanographic campaigns (based on CTD and ADCP measurements). The analysis of the in situ data shows a change in circulation from anticyclonic in October 2014 to cyclonic in June–July 2016. Furthermore, long‐term (1993–2018) analysis using gridded satellite altimetry data in the Gulf of Taranto shows that the cyclonic gyres are more frequent than anticyclonic gyres. The latter occur only for 2 to 3 years at a time in some decades

Effects of groundwater inputs to the hydraulic circulation, water residence time, and salinity in a Moroccan Atlantic Lagoon

The finite element model SHYFEM was used to study the hydrodynamics and variability of water level, salinity, temperature, and water residence time (WRT) in the Oualidia lagoon located on the Moroccan Atlantic coast. The lagoon hosts a RAMSAR convention-protected area and also offers a set of valuable ecosystem services providing the source of income for the local population. To assess the effects of submarine groundwater discharge (SGD) inputs in the study area, four simulations were set up using different SGD inputs estimates in addition to tidal forcing, bathymetry, meteorological data including solar radiation, rain, and wind, in addition to boundary conditions in the Atlantic such as salinity, water level, and water temperature. The model was calibrated and validated using hydrodynamic measurements of previous studies in 2012 and 2013. The final results from the model are in good agreement with measured data. The simulation with SGD input ~0.05 m3 s−1 produced salinity values closest to the observed ones. Calculated spatial distribution of WRT, temperature, and salinity reduced to coordinates in two PCA axes is consistent with lagoon zones developed earlier using the benthic macroinvertebrate distribution. The calculated spatial distribution of WRT allowed us to evaluate the placement of oyster aquaculture farms and small-scale fisheries in relation to water quality issues existing in the lagoon

Downscaling with an unstructured coastal-ocean model to the Goro Lagoon and the Po river delta branches

The Goro Lagoon Finite Element Model (GOLFEM) presented in this paper concentrates on the high-resolution downscaled model of the Goro Lagoon, along with five Po river branches and the coastal area of the Po delta in the northern Adriatic Sea (Italy) where crucial socio-economic activities take place. GOLFEM was validated by means of validation scores (bias – BIAS, root mean square error – RMSE, and mean absolute error – MAE) for the water level, current velocity, salinity and temperature measured at several fixed stations in the lagoon. The range of scores at the stations are: for temperature between −0.8 to +1.2◦C, for salinity from −0.2 to 5 PSU, for sea level 0.1 m. The lagoon is dominated by an estuarine vertical circulation due to a double opening at the lagoon mouth and sustained by multiple sources of freshwater inputs. The non-linear interactions among the tidal forcing, the wind and the freshwater inputs affect the lagoon circulation at both seasonal and daily time scales. The sensitivity of the circulation to the forcings was analyzed with several sensitivity experiments done with the exclusion of the tidal forcing and different configurations of the river connections. GOLFEM was designed to resolve the lagoon dynamics at high resolution in order to evaluate the potential effects on the clam farming of two proposed scenarios of human intervention on the morphology of the connection with the sea. We calculated the changes of the lagoon current speed and salinity, and using opportune fitness indexes related to the clams physiology, we quantified analytically the effects of the interventions in terms of extension and persistence of areas of the clams optimal growth. The results demonstrate that the correct management of this kind of fragile environment relies on both long-term (intervention scenarios) and short-term (coastal flooding forecasts and potential anoxic conditions) modeling, based on a flexible tool that is able to consider all the recorded human interventions on the river connections. This study also demonstrates the importance of designing a seamless chain of models that are capable of integrating local effects into the coarser operational oceanographic models

Sediment transport in a tidal inlet: the case of the Lido Inlet, Venice, Italy

Tidal inlets provide a connection between the ocean and bays, lagoons, marshes, and tidal creek systems. Two hydrodynamic factors are dominant in the long term evolution of a tidal inlet: wind waves, that are mainly responsible for re-suspending sediments, and tidal currents, that maintain the main inlet channel by advecting sediments away from the inlets. These two factors determine to a large extent the direction and magnitude of sediment transport. Tidal inlets, however, are often radically modified by human-driven intervention (for example for navigation or protection purposes). This is the case of the three inlets of the Venice Lagoon, Italy, that are now the main construction site of a mobile barrier system for the protection of the historical city of Venice from floods. In September 2014, an experiment was set up in one of the lagoon inlets aimed to quantify the bedload transport inside the inlet channel over a tidal cycle. To obtain a bedload transport estimate, we carried out repeated bathymetric surveys inside the inlet channel during a tidal cycle using a high resolution Multibeam Echosounder System. The tidal currents and water column transport were measured with ADCP calibrated by water samples. At the same time, sediment traps were deployed at the channel bottom and grab samples were collected. The preliminary results of the experiment show evidence of net transport over a tidal cycle. Comparing repeated bathymetric surveys over different years we find substantial changes in the inlet channel morphology

Marine rapid environmental assessment in the gulf of Taranto: A multiscale approach

A multiscale sampling experiment was carried out in the Gulf of Taranto (eastern Mediterranean) providing the first synoptic evidence of the large-scale circulation structure and associated mesoscale variability. The mapping of the mesoscale and large-scale geostrophic circulation showed the presence of an anticyclonic large-scale gyre occupying the central open ocean area of the Gulf of Taranto. On the periphery of the gyre upwelling is evident where surface waters are colder and saltier than at the center of the gyre. Over a 1-week period, the rim current of the gyre undergoes large changes which are interpreted as baroclinic-barotropic instabilities, generating small-scale cyclonic eddies in the periphery of the anticyclone. The eddies are generally small, one of which can be classified as a submesoscale eddy due to its size. This eddy field modulates the upwelling regime in the gyre periphery