AN EFFICIENT HORIZONTAL ADVECTION SCHEME FOR THE MODELING OF GLOBAL TRANSPORT OF CONSTITUENTS

In this paper the authors consider a dimensional-splitting scheme for horizontal advection on a sphere with a uniform longitude-latitude gri d. The 1D subprocesses that arise within the splitting are solved with an explicit finite-volume type scheme, which is made unconditionally stable by allowing the stencil to vary with tile Courant numbers. The scheme is made positive by flux limiting. For the inaccuracies at the poles some special measures are discussed. Numerical tests show that t he scheme is almost shape preserving and conservative, and it gives ac curate results at low computational costs.