Author(s)

C. Walcek

Abstract

A simple but very accurate method for calculating advection of mixing ratios in a mass conservative and monotonic manner is presented. This scheme uses a second-order accurate flux approximation with a minor adjustment surrounding local maximums and minimums that greatly reduces numerical diffusion. For many standard advection tests, advection errors are typically 1/2 to 1/3 the errors of the most accurate monotonic advection schemes used today. The scheme is positive-definite, but negative values can be advected with no modifications. A generalized algorithm for advecting mixing ratios through variable-spaced grids of one to three dimensions, including strongly deformational flows, is presented. A FORTRAN code for testing the algorithm in 1-

Keywords