Abstract
A criterion for the instability of shearing gravitational waves on the discontinuous interface between a two-isothermal-layer is derived from the result of Bjerkness et al. Comparison of this criterion with the Richardson number gives the results that in the present model the critical Richardson number is ½ and the vertical extent of the turbulent layer is estimated to reach 1/2(π) of the wavelength. Various observed data in actual clear air turbulence are used to evaluate these two constants.
