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This work describes the design and validation of a high-resolution (1/36°) ocean forecasting model over the "Iberian-Biscay-Irish" (IBI) area. The system has been setup using the NEMO model (Nucleus for European Modelling of the Ocean). New developments have been incorporated in NEMO to make it suitable to open- as well as coastal-ocean modelling. In this paper, we pursue three main objectives: (1) to give an overview of the model configuration used for the simulations; (2) to give a broad-brush account of one particular aspect of this work, namely consistency verification; this type of validation is conducted upstream of the implementation of the system before it is used for production and routinely validated; it is meant to guide model development in identifying gross deficiencies in the modelling of several key physical processes; and (3) to show that such a regional modelling system has potential as a complement to patchy observations (an integrated approach) to give information on non-observed physical quantities and to provide links between observations by identifying broader-scale patterns and processes. We concentrate on the year 2008. We first provide domain-wide consistency verification results in terms of barotropic tides, transports, sea surface temperature and stratification. We then focus on two dynamical subregions: the Celtic shelves and the Bay of Biscay slope and deep regions. The model-data consistency is checked for variables and processes such as tidal currents, tidal fronts, internal tides and residual elevation. We also examine the representation in the model of a seasonal pattern of the Bay of Biscay circulation: the warm extension of the Iberian Poleward Current along the northern Spanish coast (Navidad event) in the winter of 2007-2008. [ABSTRACT FROM AUTHOR]

We develop and implement a new method to take into account the impact of waves into the 3-D circulation model SYMPHONIE (Marsaleix et al., 2008, 2009a) following the simplified equations of Bennis et al. (2011), which use glm2z-RANS theory (Ardhuin et al., 2008c). These adiabatic equations are completed by additional parameterizations of wave breaking, bottom friction and wave-enhanced vertical mixing, making the forcing valid from the surf zone through to the open ocean. The wave forcing is performed by wave generation and propagation models WAVEWATCH III® (Tolman, 2008, 2009; Ardhuin et al., 2010) and SWAN (Booij et al., 1999). The model is tested and compared with other models for a plane beach test case, previously tested by Haas and Warner (2009) and Uchiyama et al. (2010). A comparison is also made with the laboratory measurements of Haller et al. (2002) of a barred beach with channels. Results fit with previous simulations performed by other models and with available observational data. Finally, a realistic case is simulated with energetic waves travelling over a coast of the Gulf of Lion (in the northwest of the Mediterranean Sea) for which currents are available at different depths as well as an accurate bathymetric database of the 0-10 m depth range. A grid nesting approach is used to account for the different forcings acting at different spatial scales. The simulation coupling the effects of waves and currents is successful to reproduce the powerful northward littoral drift in the 0-15 m depth zone. More precisely, two distinct cases are identified: When waves have a normal angle of incidence with the coast, they are responsible for complex circulation cells and rip currents in the surf zone, and when they travel obliquely, they generate a northward littoral drift. These features are more complicated than in the test cases, due to the complex bathymetry and the consideration of wind and non-stationary processes. Wave impacts in the inner shelf are less visible since wind and regional circulation seem to be the predominant forcings. Besides, a discrepancy between model and observations is noted at that scale, possibly linked to an underestimation of the wind stress. This three-dimensional method allows a good representation of vertical current profiles and permits the calculation of the shear stress associated with waves and currents. Future work will focus on the combination with a sediment transport model. [ABSTRACT FROM AUTHOR]

We develop and implement a new method to take into account the impact of waves into the 3-D circulation model SYMPHONIE (Marsaleix et al., 2008, 2009a), following the simplified equations of Bennis et al. (2011) which use glm2z-RANS theory (Ardhuin 5 et al., 2008b). These adiabatic equations are completed by additional parameterizations of wave breaking, bottom friction and wave-enhanced vertical mixing, making the forcing valid from the surf zone through to the open ocean. The wave forcing is performed by wave generation and propagation models WAVEWATCH III® (Tolman, 2008, 2009; Ardhuin et al., 2010) and SWAN (Booij et al., 1999). The model is tested and 10 compared with other models for a plane beach test case, previously tested by Haas and Warner (2009) and Uchiyama et al. (2010). A comparison is also made with the laboratory measurements of Haller et al. (2002) of a barred beach with channels. Results fit with previous simulations performed by other models and with available observational data. 15 Finally, a realistic case of energetic waves travelling over a coast of the Gulf of Lion (in the northwest of the Mediterranean Sea) for which currents are available at different depths as well as an accurate bathymetric database of the 0-10m depth range, is then simulated. A grid nesting approach is used to account for the different forcings acting at different spatial scales. The simulation coupling the effects of waves and 20 currents is successful to reproduce the powerful northward littoral drift in the 0-15m depth zone. More precisely, two distinct cases are identified: when waves have a normal angle of incidence with the coast, they are responsible for complex circulation cells and rip currents in the surf zone, and when they travel obliquely, they generate a northward littoral drift. These features are more complicated than in the test cases, due 25 to the complex bathymetry and the consideration of wind and non-stationary processes. Wave impacts in the inner shelf are less visible since wind and regional circulation seem to be the predominant forcings. Besides, a discrepancy between model and observations is noted at that scale, possibly linked to an underestimation of the wind stress. Lastly, this three-dimensional method allows a good representation of vertical current profiles and permits to calculate the shear stress associated with wave and current. Future work will focus on the combination with a sediment transport model. [ABSTRACT FROM AUTHOR]

An embedded forecasting system was developed for the North-Western Mediterranean at 3-km resolution. The system is based on the Symphonie hydrodynamic free surface model and on the variational initialization and forcing platform VIFOP. The regional model is initialized and forced at its open lateral boundaries by the MFS GCM and forced at the surface by the ALADIN numerical weather prediction model. Once a week, a five-day forecast is produced after a hindcast of seven days. This pre-modeling period of 7 days before beginning the forecast allows the development of the small scale features associated to the high resolution. The relevance of the 5-day forecast strategy has been examined by comparing the forecasted fields to hindcast fields (forced by meteorological and oceanic analyses) considered as a reference. Mismatches remain at a very low level indicating a good quality of the forecasted forcing fields and also possibly to the strong wind conditions which prevailed during the period. The embedded forecasts have been compared to the MFS observing system (SST and MedArgo) during 6 forecast cycles between September 2004 and February 2005. It was basically found that in the North-Western Mediterranean, the MFS basin-scale model and thus the regional model forecasts are characterized by large negative biases of salinity in the first 100m under the surface leading thus to too light subsurface waters. The underestimation of temperature by the regional model just below the surface and its overestimation at 30m deep can be attributed to an overestimation of the turbulent mixing. The regional model allows to represent a number of processes especially those induced by the wind as coastal upwelling under stratified conditions, dense water formation over the Gulf of Lion shelf, deep mixing in the convection zone or influence on the Northern Current penetration in the Gulf of Lion. [ABSTRACT FROM AUTHOR]

Abstract: The upper circulation in the southern Bay of Biscay is analysed over winter and fall 2004 using a coastal altimetric dataset, moorings, sea surface temperature (SST) observations and a regional simulation from the SYMPHONIE model. The aim is to determine whether altimetric data can detect occurrences of a slope current (the Iberian Poleward Current, IPC). We first analyse in situ and SST data. The results show pulses of a warm surface poleward flow (IPC) limited to the westernmost part of the northern Spanish coast. Along-track TOPEX/Poseidon and Jason-1 data are analysed over three ‘events’ (Jan., Feb., and Oct. 2004). Altimetric data can depict the main pulses. They provide some information on their spatial variability but the present in situ dataset is not dense enough to assess this information. Local inconsistencies between neighbouring tracks may be related to uncertainties in altimetric corrections. The simulated fields are consistent with the in situ observations. They allow us to better understand the IPC subsurface properties and its signature in altimetric data. The ability of altimetry to monitor IPC pulses under any atmospheric conditions or when the SST signature is weak makes it an essential component for the IPC observing system in addition to satellite SST and moorings data. [Copyright &y& Elsevier]

Abstract: The generation of internal tides in the ocean is due to the interaction of strong barotropic tidal currents with variable topography in stratified waters, transferring energy from the external to the deep ocean. The internal tides feed later the ocean mixing, playing a major role for the maintenance of the stratification of the global ocean. A remarkable region in terms of tidal energy is the European continental shelf. As a first step toward the study of internal tides in the Bay of Biscay, this paper aims at understanding the barotropic tides and associated energy budgets. On continental shelves and in coastal seas the use of regional models with fine grid resolution is preferred to the use of global tidal atlases derived from altimetry. The unstructured grid T-UGOm model is used to compute the NEA-2004 tidal solutions in the North-East Atlantic ocean, with errors greatly reduced in coastal areas compared with global models. Energy budgets are discussed based on the inclusion of nonlinearities in the tidal solutions. The sea surface height and depth-averaged currents are used to compute the tidal energy conversion from barotropic to baroclinic tides, tidal dissipation and energy flux. A total amount of energy of 250GW is found for the tide. The path of energy from the Southern Atlantic ocean toward the Bay of Biscay is highlighted, advocating for nonzero boundary conditions in regional models. The 3D coastal ocean SYMPHONIE model has been implemented to simulate the surface tides in the Bay of Biscay. Solutions are validated by comparison with the NEA-2004 solutions and observations. [Copyright &y& Elsevier]