Lionello, P. (University of Padua, Italy)
Malguzzi, P. (FISBAT-CNR, Bologna, Italy)
In this study, the atmospheric circulation, the ocean waves and the sea circulation are simultaneously modelled.
Specifically, the importance of the two-way coupling between atmosphere and ocean is discussed.
This is an hindcast study applied to the medium range regional prediction. The analysed weather and sea evolution is represented by the development of an intense low pressure moving over Italy which generates high ocean waves and storm surge, which is associated with the flooding of Venice.
The whole model structure consists of three modules: BOLAM, WAM and POM. The BOLAM model (BOlogna Limited Area Model, Buzzi et al. 1993), recently developed at FISBAT, is a complete mesoscale meteorological, grid-point model. It integrates the hydrostatic primitive equations on a limited area domain and includes treatment of surface fluxes, radiation and parameterization of deep convection. The POM model (Princenton Ocean Model, Blumberg A.F. and G.L. Mellor 1987) is an ocean circulation model that solves the hydrostatic primitive equations with a free surface, curvilinear horizontal coordinates, vertical sigma coordinate, free surface and a second order closure scheme for the computation of the vertical mixing. This study uses only the external (barotropic) mode. The WAM (WAve Model, The WADMI Group 1988) model describes the evolution of the wave spectrum by solving the wave energy transfer equation with no constraints on the spectral space.
This model set-up is capable of the high space and time resolution required by the complex orography surrounding the Mediterranean Sea, the short duration of the storm and the short and variable fetch. It has, moreover, two main advantages: it allows the coupling and the crossvalidation of the models. In fact, the model accounts for the interaction between the ocean waves on the surface stress (Janssen 1991). The comparision of the model results against the measurements of pressure, wind, wave, men sea level and air temperature gives independent validation of the model output.