The Canadian MC2 mesoscale model provided 3-km daily forecasts across the Alps during the entire MAP field phase of 1999 (Benoit et al., BAMS January 2002). At the time, the mesh-size average of topographic height was further low-pass filtered at 3-delta x to control the strength of the terrain forcing on the model semi-implicit semi-Lagrange dynamics. Since then, a new terrain-following coordinate was designed and tested in the MC2 by Schaer et al. (2002) to reduce the amount and the small scales of the orographic signature present on the upper atmosphere coordinate surfaces.

Also, a relaxation of the basic isothermal state required for the semi-implicit discretization of the full flow has been made and tested succesfully for the linear mountain flow problem examined in Schaer et al. The impact of this change on selected MAP-SOP simulations is described.