Application of WKB Theory to Turbulence Layers in the Vicinity of Critical Levels

[摘要] Viscous dissipation and Newtonian cooling suppress the breaking of internal gravity waves particularly in the vicinity of the critical levels. Stabilization criteria for suppressing wave breakdown are obtained incorporating the effects of viscous dissipation and Newtonian cooling separately when the basic Richardson number is large. The stabilization criterion associated with viscous dissipation derived here is more consistent than that obtained by Fritts and Geller (1976). Newtonian cooling, which is less important for the short horizontal wavelength, predominates over viscosity as the horizontal wavelength increases. Both effects become comparable when the horizontal wavelength is about 250 km in the stratosphere and is much longer in the mesosphere.Characteristics of internal gravity waves at 20km altitude such as wave amplitude and momentum flux are estimated on the basis of the thickness of the turbulence layer observed in the lower stratosphere.

[学科分类] 大气科学