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  • Exceptional Bora outbreak i...
    Davolio, Silvio; Stocchi, Paolo; Benetazzo, Alvise; Bohm, Emanuele; Riminucci, Francesco; Ravaioli, Mariangela; Li, Xiao-Ming; Carniel, Sandro

    Dynamics of atmospheres and oceans, September 2015, 2015-09-00, 20150901, Volume: 71
    Journal Article

    •Exceptional Bora event of winter 2012 over the northern Adriatic is investigated.•NWP model (BOLAM–MOLOCH) simulations are validated and discussed.•Near-surface meteorological variables, SST and surface fluxes are analyzed.•SST initialization strongly impacts surface fluxes prediction.•Possible model improvements are identified. The Bora wind event occurred in winter 2012 was exceptional in terms of both meteorological effects and impact on the Adriatic Sea circulation. It was associated with intense and persistent winds, very cold temperatures all over the Mediterranean basin and heavy snowfall over the Apennines slopes exposed to north-easterly winds, and it was responsible for triggering dense water formation and driving basin-scale oceanic circulation. The cooling period (29 January–13 February) was characterized by intense air–sea exchanges of momentum and heat, whose accurate simulation is required for a proper description of atmospheric and ocean circulations. In the present study, results of a number of short-range high-resolution numerical weather prediction (NWP) model simulations for the entire Bora outbreak are discussed. The modeling chain, based on BOLAM and MOLOCH limited area models, has been implemented using initial and boundary conditions provided by different global NWP systems. Model performance has been evaluated in terms of variables of interest for oceanographic applications, such as sea surface temperature (SST), surface heat fluxes, solar radiation and near surface meteorological parameters (air temperature, wind, pressure and humidity). The validation has been undertaken through a comparison against surface data (buoys and oceanographic platforms) available at different locations in the northern Adriatic area, while advanced synthetic aperture radar (ASAR) products have been used to assess modeled wind fields on a larger scale. Model results indicate a good agreement with the observations concerning meteorological variables, in particular wind, pressure and temperature. However, large differences were found in the SST forecasts, which in turn affect also sea surface flux predictions. The uncertainties in SST forecasts are mainly ascribable to the different initialization fields provided by either the global models or satellite analyses. Thus SST initialization represents a critical issue for an accurate description of surface fluxes at least for this exceptionally severe event.