An implicit formulation for horizontal diffusion in gridpoint models

Abstract

An implicit formulation that is unconditionally stable is proposed for gridpoint models. It is tested in a tridimensional hemispheric model. The model is integrated to 5 days with various values of the coefficient of diffusion. All forecasts are verified, and the value of the coefficient that gives the best score is retained. It is found that this optimum value is larger than the values commonly used in most models. These values are used strictly to test the proposed implicit formulation. -from Authors