Coastal ocean forecasting with an unstructured-grid model in the Southern Adriatic Northern Ionian Sea

Abstract

Abstract. SANIFS (Southern Adriatic Northern Ionian coastal Forecasting System) is a coastal-ocean operational system based on the unstructured-grid finite-element three-dimensional hydrodynamic SHYFEM model and providing short-term forecasts. The operational chain is based on a downscaling approach starting from the large-scale system for the entire Mediterranean basin (MFS, Mediterranean Forecasting system), which provides initial and boundary condition fields to the nested system. The model is configured to provide hydrodynamics and active tracer forecasts both in open ocean and coastal waters of South-eastern Italy using a variable horizontal resolution from 3–4 km in the open sea to 500–50 m in the coastal areas. Given that the coastal fields are driven by a combination of both local/coastal and deep ocean forcings propagating along the shelf, the performance of SANIFS was verified both in forecast and simulation mode, first (i) at the large and shelf-coastal scales by comparing with a large scale survey CTD in the Gulf of Taranto and then (ii) at the coastal-harbour scale (Mar Grande of Taranto) by comparison with CTD, ADCP and tide gauge data. Sensitivity tests were performed on initialization conditions (mainly focused on spin-up procedures) and on surface boundary conditions by assessing the reliability of two alternative datasets at different horizontal resolution (12.5 and 6.5 km). The SANIFS forecasts at a lead-time of one day were compared with the MFS forecasts highlighting that SANIFS is able to retain the large scale dynamics of MFS. Those get correctly propagated to the shelf-coastal scale improving the forecast accuracy (+17 % for temperature and +6 % for salinity compared to MFS). Moreover the added value of SANIFS was assessed at coastal-harbour scale, which is not covered by the coarse resolution of MFS, where the SANIFS forecasted fields well reproduced the observations (temperature RMSE equal to 0.11 °C). Furthermore SANIFS simulations were compared with hourly time-series of temperature, sea level and velocity measured at the coastal-harbour scale showing a good agreement. Simulations in the Gulf of Taranto described a circulation mainly characterized by an anticyclonic gyre with the presence of cyclonic vortexes in shelf-coastal areas. A surface water inflow from open sea to Mar Grande characterizes the coastal-harbour scale.

River runoff influences on the Central Mediterranean overturning circulation

“…The profiles are in the area of deep water formation and in the northern Ionian exit, so in the most relevant places for our simulations. On the whole, EXP1 is in good agreement with the observed data, comparable RMSE and BIAS values were found for different models of the Adriatic Sea (Guarnieri et al 2013) and the Ionian Sea (Federico et al 2016;Kassis et al 2016). In EXP2 without rivers, water masses in the Adriatic Sea appear saltier and warmer with respect to the observed dataset.…”

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

“…The effect induced by the counterclockwise circulation at the surface in Mar Grande is also in accordance with the comparison at the ADCP transects as reported in Table 3: a negative mean flux exiting the Mar Grande basin is observed both in measurements and computations; discharges along the sections are also well reproduced by the model, along with the mean flux velocities and directions. The presented results also agree, as well as with the available measurements, with the findings by De , that described the 2013-averaged fields of Mar Grande, while SANIFS outputs in Federico et al (2016) reported opposite circulation and fluxes.…”

“…Indeed, the harmonic analysis of the wa- ter elevation on an hourly basis was performed using the TAPPY tidal analysis package (Cera, 2011), and the results for the most important semidiurnal and diurnal constituents (M2, K1) were compared to observations. This analysis reports errors of 6.9 and 5.8 % for amplitude and phase of the K1 component, and errors of 3.7 and 2.2 % for amplitude and phase of the M2 component, showing very accurate results in comparison with other reference studies (Ferrarin et al, 2013;Federico et al, 2016).…”

“…The model is forced (i) at the two lateral open boundaries through a full nesting strategy directly with the MFS (temperature, salinity, sea surface height and currents) and OTPS (tidal forcing) fields; and it is forced (ii) at the sea surface through two alternative atmospheric forcing datasets (ECMWF, 12 km, and COSMOME, 6 km) via MFS bulk formulae (e.g., Pinardi et al, 2003;Castellari et al, 1998). SANIFS features have been validated in Federico et al (2016) comparing model results with observed data.…”

Meteo and Hydrodynamic Measurements to Detect Physical Processes in Confined Shallow Seas

“…Predictive operational oceanography commonly uses models covering regional, sub-regional and shelf-coastal scales. To study local scales, with a resolution of a few hundred meters, multiscale modelling systems, based on a multiple-nesting approach, have been implemented lately [ 8 , 9 , 11 , 12 ]. In all cases, they require calibration and validation with measured data.…”