Seamless and cross-scale modelling of the ocean: from regional to shelf-coastal and urban scale

Ivan Federico1, Ivano Barletta2, Giorgia Verri3, Fabio Montagna1, Salvatore Causio1, Giovanni Coppini4, Emanuele Di Lorenzo5 and Nadia Pinardi6, (1)CMCC - EuroMediterranean Center on Climate Change, Lecce, Italy, (2)CMCC - EuroMediterranean Center on Climate Change, Italy, (3)CMCC, Ocean application and Prediction Division, Lecce, Italy, (4)Euro-Mediterranean Center on Climate Change, Ocean Predictions and Applications, Lecce, Italy, (5)Georgia Inst Tech, Earth and Atmospheric Sciences, Atlanta, GA, United States, (6)University of Bologna, Bologna, Italy
The present work shows the development and implementation of 3D-thermo-hydrodynamic fully-baroclinic modelling systems, based on the unstructured-grid finite-element SHYFEM model and solving with appropriate and variable resolution different oceanographic scales.

The first implementation is UMEDBS (Unstructured-grid MEDiterranean and Black Sea), covering the entire Southern European Seas (Mediterranean and Black Sea) with a unique continuum grid, and focused both on the regional and shelf-coastal scale. The model domain extends in an Atlantic box with a lateral open boundary nested into high-resolution global ocean model (GOFS16). The horizontal resolution is optimized on the local bathymetry, coastline and expected solutions (relevant dynamics and coastal scale features), and ranges from 4-5 km in open-ocean to 1km-500m in overall shelf-coastal seas to 50-60m in narrow straits (Dardanelles and Bosphorus). The model has been run in hindcast and free-active mode and compared with satellite observations and in-situ coastal observations showing good agreement. The impact of straits (Gibraltar, Sicily, Otranto, Dardanelles, Bosphorus) on the dynamics and exchanges of interconnected basins (e.g. Black Sea, Marmara Sea end Eastern Mediterranean Sea) have been investigated. Furthermore, model inter-comparison has been performed with GOFS16 and MFS (Mediterranean Forecast System products of CMEMS European Service, analysis.

The further implementation here presented is a test-bed of CMEMS downscaling in non-EU area. A modelling system has been designed to provide high- and hyper- resolution forecasts for the Georgia (U.S.A.) coasts, with specific focus and grid refinement in riverine and port area of Savannah city, including the marshland zones and model wet-and-dry capabilities. The horizontal resolution ranges from 1-2km in open ocean to 10m in the urban area of interest. The modelling system is laterally forced in terms of (i) 3D thermo-hydro dynamics by CMEMS GLO-MFC - Global Monitoring and Forecasting Center - and (ii) tides by OTPS – Oregon State University Tidal Prediction Software. The model performances have been evaluated in forecasting mode simulating extreme events (Metthew and Dorian hurricanes), showing good agreement with in-situ mooring station.