Dealing with the Bottom Intersection Problem in Isopycnic-Coordinate Models Using the Flooding Algorithm

Abstract

In isopycnic-coordinate models, special algorithm is required to compute the horizontal pressure force on steep bottom slopes. The “extrapolation” algorithm which constructs an “underground” estimate of pressure force using extrapolation was used in previous studies to deal with the bottom intersection problem. However, extrapolation will definitely introduce some errors, and would not be the best way to deal with this problem. In this paper, the flooding algorithm which is traditionally used to simulate transient flooding of coastlines caused by tides or tsunamis is used in the isopycnic-coordinate model to deal with the bottom intersection problem. The two algorithms were compared in the test case with a two-dimensional isolated Gaussian topography. The results of comparison indicate that the flooding algorithm performs better in dealing with the bottom intersection problem especially with the situation where interfaces near the bottom topography are going upwards.