Stratopsheric drag is applied in two ways. Firstly, using a simple formulation as a Rayleigh damping near the top of the model (SDRAG). Secondly, and generally only if the stratsophere is being properly resolved, we have a physically-based estimate of gravity-wave drag detemined from the model simulation of moist convection, mountain waves, shear and deformation (in STRATDYN) (Rind et al, 1988). When gravity waves break, there is also some vertical mixing associated with that. Both GWDRAG and SDRAG are applied within the dynamical leap frog tiome steps to improve stability.