Techniques for the study of gravity waves and turbulence (keynote paper), part 4

Probably one of the most important achievements mesosphere stratosphere troposphere (MST) radars can make toward increasing the understanding of the dynamics of the atmosphere is to determine the exact relationship between the generation of turbulence and the sources of high shear or convectively unstable flows. An important theoretical tool, the gravity-wave breaking through which one can begin to understand spontaneous generation of turbulence model is discussed. In this model, large amplitude gravity waves produce local regions where the Richardson number (N sup 2/U sub Z sup 2) is less than 1/4 thus giving rise to turbulent flows. Thus the appearance of turbulent layers can often be interpreted as a breaking-gravity-wave signature. Even though the techniques for studying gravity waves and turbulence may be quite different (and historically have resulted in somewhat separate bodies of literature), it is clear from the wave-breaking model that the phenomena are intimately linked. The techniques for measurements of gravity wave flow fields and turbulent regions by MST radar should show cognizance of some of the theoretical questions raised by the wave-breaking model.