Idealized COAWST model cases for studying the comparison of physical to numerical mixing with different tracer advection schemes in estuarine environments.

The numerical simulation of estuarine dynamics requires accurate prediction for the transport of tracers such as temperature and salinity. All numerical models introduce two kinds of tracer mixing: 1) by parameterizing the tracer eddy diffusivity through turbulence models leading to a source of physical mixing and 2) discretization of the tracer advection term that leads to numerical mixing. Both physical and numerical mixing vary with the choice of horizontal advection schemes, grid resolution, and time step. We utilize the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) model to study the mixing in the model by simulating four idealized cases with three different tracer advection schemes.