We analyze in the L-infinity-norm a class of semi-Lagrangian advective sche
mes introduced by the author and A. Staniforth in 1992 to improve the solut
ion produced by numerical models for weather prediction and climate studies
that use semi-Lagrangian advective schemes. The new quasimonotone and cons
ervative semi-Lagrangian schemes are L-infinity-stable and converge optimal
ly when the solution is sufficiently smooth.