Non-hydrostatic pressure in sigma-coordinate ocean models

作者：Keilegavlen Eirik^*; Berntsen Jarle

来源：Ocean Modelling, 2009, 28(4): 240-249.

DOI：10.1016/j.ocemod.2009.02.006

• Non-hydrostatic pressure
• sigma-Coordinates
• Internal waves

Numerical ocean modelling is computationally very demanding. Traditionally, the hydrostatic approximation has been applied to reduce the computational burden. This approximation is valid in large scale studies with coarse grid resolution. With faster computers and gradually smaller grid sizes, we may expect that more studies will be performed with non-hydrostatic ocean models. In recent papers several methods for including non-hydrostatic pressure in or-coordinate models have been suggested. In this paper the sensitivity of the non-hydrostatic pressure field, the velocity fields, and the density fields to changes in the method for computing non-hydrostatic pressure in sigma-coordinate ocean models is addressed. The first test case used involves the propagation and breaking of an internal wave at an incline in a tank. The other test case concerns tidally driven flow over a sill in a stratified fjord. The results from our numerical exercises suggest that the velocity and density fields are very robust to the model choices investigated here. The differences between the model results are of the same order as the uncertainty due to the internal pressure gradient error, and they are smaller than an estimate of the uncertainty due to subgrid scale closure.

• 出版日期2009