turbulent closure parameter identification for the surface layer of marine circulation models. – TURBIDENT

Fluxes between the oceanic surface layer and atmosphere is one of the main difficulty to solve so as to ensure realistic results for the numerical models of marine circulation. This is particularly true in the coastal region. Indeed, the upper mixing layer is often a weakness of numerical modelling in the vicinity of the air-sea interface. This is due to the great difficulty to obtain reliable and accurate measurements for that range of immersion. Yet, this layer controls the vertical turbulent transfert of any substance brougth – e.g. - either by eolian transport or by terrigeneous river input (or by any other way). Then, there is a great chalenge to better define parameters of turbulent closure schemes of marine circulation models in the coastal zone, for the civil or the military use. This is the goal of the TURBIDENT project, which aims at optimizing the functionning parameters of these turbulent closure models owing to an assimilation of an original and well-suited set of data. It consists of HF radar measurements of marine surface currents associated with high resolution acoustic Doppler current profile in the close sub surface layer. The optimization technique is also new in itself. Although being a variational identification method, there is no need to resort to the traditional (and heavy) adjoint method to evaluate the required quantities for the minimization algorithm of the objective cost function which measure the model-data discrepancy.
Key word : variational data assimilation, marine current measurements, surface layer, turbulent closure, numerical model of coastal circulation.