A front-resolving sigma coordinate sea model with a simple hybrid advection scheme

Abstract

A three-dimensional sigma coordinate finite difference numerical model with a free surface is applied to the problem of eddy growth on marine fronts. It gives similar results to those of a previous rigid lid model, predicting, in particular, the appearance of an anticyclonic 'whirl' in a flow resembling the Norwegian coastal current. Three advection schemes are considered; these are upwind differencing, which introduces numerical diffusion, centred differencing, which introduces spurious density values and ripples near the front, and a hybrid scheme, retaining the positivity of the upwind scheme but reducing the numerical diffusion. © 1986.