Shelf slope, estuarine dynamics and river plumes in a z* vertical coordinate, unstructured grid model

The finite element, unstructured grid model SHYFEM has been used to carry out some fundamental studies on the quality of a specific type of Generalized Vertical Coordinate (GVC) system, the so-called z* coordinates versus z - geopotential coordinates. Idealized and realistic test cases are shown to assess the impact of the vertical coordinates on key physical processes, i.e. the internal tide generation at a continental slope, a river plume shape and intensity and the salt water intrusion. The results showed that the z* coordinates produce a stronger water column stratification than the z - geopotential ones and together with the unstructured grid modeling they can better solve the coastal sea dynamics. An idealized twin experiment configuration of the model was carried out to verify the proper implementation of the GVC z* by simulating the production of internal tides at the continental slope. The results confirmed that the z* coordinate model reproduces the expected internal tide fields better than z - geopotential model. A set of realistic experiments in the Po river delta coastal region, demonstrated that the representation of the dynamical processes at the coastal scales is conditioned by the high resolution (25 cm layers), which was only possible by the z* formulation in the upper water column.