A tidally averaged stochastic transport model

This paper presents a tidally averaged model that approximates the long-term mixing processes of dissolved matter in tidal waters. The averaged transport model is based on a stochastic particle model. Because formal averaging techniques are used, the asymptotic validity of the approximation can be proven under the restriction that the diiusion coeecient is small. Numerical implementation of the averaging procedure results in a numerical eld of Lagrangian residual ow velocities and an-isotropic diiusion tensors. These diiusion tensors contain the main tidal dispersive processes. The Lagrangian residual ow-eld and the diiu-sion tensor eld are the parameters that determine the tidally averaged stochastic transport model. The averaging procedure is applied to a model of the Dutch Coastal zone. Results of simulations with the tidally averaged model are compared with those of the tidal model. This comparison shows that the results of the averaged computer model are accurate while, at the same time, the computation time is reduced with an order of magnitude.