The Effect of Horizontal Grid Resolution in an Atmospheric Circulation Model

Abstract

Truncation error of the numerical solution in a circulation model is still one of the most serious sources of error for the extended-period prediction. Different grid intervals are taken and the behavior of the solution is studied empirically. The meshes for the hemispheric domain are N=20, 40 and 80, where N is the number of grid points between the pole and the equator on the stereographic projection map. Analysis revealed that finer meshes provide clearly better solutions even for the planetary-scale mode, and the N=80 solution is definitely different from the N=40 beyond about 6 days. Further comparisons were made to see if the N=80 solution is actually closer to observation. The results were encouraging. Promise is seen for improvement in the forecast to about 10 days. The inclusion of subgrid-scale eddy viscosity, which seems to be necessary when applying a grid to the flow field, is also examined.