Two-ways, doubly nested primitive equation model of the Ligurian Sea

In the framework of the SOFT project (Satellite-based Ocean ForecasTing), the GHER 3D primitive equation model is implemented in its double nesting version. A low res- olution model (15 ) simulates the circulation in the Mediterranean Sea. This model provides the boundary conditions for an intermediate resolution model (3 ) located in the Gulf of Lions and the Ligurian Sea. The next nesting level is a one-minute resolu- tion model centered in the Ligurian Sea. Each "child" model depends on its "parent" model by the boundary conditions. At each time step the mean values of the "child" model are also injected in the "parent" model. The conservation laws require the inter- polation of the boundary values to be consistent with the finite volume discretisation of the model. A method taking also into account the difference of the land-sea mask in the "child" and "parent" model, will be discussed.
The models run over a time period of 1 months starting the 1st January 1999. The output of the high resolution model is compared with the Sea Surface Temperature measured by the ATSR-2. The results show that nested and two ways coupled models are a powerful approach to solve open boundary problems and to use different grid resolutions in a numerically efficient way.