BALANCED WIND IN ADVANCED ADVECTION SCHEMES WHEN SPECIES WITH LONG LIFETIMES ARE TRANSPORTED

Advanced numerical schemes are often used for the advective transport in chemical transport models. The numerical errors associated with the different schemes are low, but still noticeable especially when species with long lifetimes are advected. The errors can be divided into two: the intrinsic error from the operator splitting and the discretization errors associated with the operator approximations. It is shown that the combined effect can lead to errors in the transport of 20% in a 48 h integration, and that the errors are often difficult to detect when the schemes are tested. A simple and effective method in which the model's advection scheme is used to balance the wind velocities is suggested.