VISCOUS STABILIZATION OF GRAVITY WAVE CRITICAL LEVEL FLOWS.

A criterion for the viscous stabilization of gravity wave critical level flow is derived to be Z// one quarter less than equivalent to 2. 5Z// nu , where Z// one quarter is the vertical thickness of the unstable region in the vicinity of a gravity wave critical level calculated with an inviscid linear theory and Z// nu is the viscous length scale for gravity wave critical level interaction. The stability implications of this criterion are examined for gravity wave critical level flows in the laboratory, the atmospheric planetary boundary layer, the upper atmosphere and the ocean thermocline region.