Generation of Turbulence by Atmospheric Gravity Waves

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Abstract
The standard current criterion for the generation of turbulence by atmospheric gravity waves and for the associated limitation on wave growth is based upon the standard criterion for static instability of the unperturbed atmosphere, namely, that the vertical gradient of potential temperature be negative. This criterion fails to recognize that a slantwise static instability may be available in the presence of gravity waves and, if so, could be of importance. New criteria, involving estimated growth times, are developed here and reveal slantwise instability to be a likely mechanism of turbulence production. It is also found that the most favored axes for the development of the slantwise instability are quasi-horizontal, which suggests that the resultant turbulent motions may well be quasi-horizontal, at least at the energy-input portion of the turbulence spectrum. Abstract The standard current criterion for the generation of turbulence by atmospheric gravity waves and for the associated limitation on wave growth is based upon the standard criterion for static instability of the unperturbed atmosphere, namely, that the vertical gradient of potential temperature be negative. This criterion fails to recognize that a slantwise static instability may be available in the presence of gravity waves and, if so, could be of importance. New criteria, involving estimated growth times, are developed here and reveal slantwise instability to be a likely mechanism of turbulence production. It is also found that the most favored axes for the development of the slantwise instability are quasi-horizontal, which suggests that the resultant turbulent motions may well be quasi-horizontal, at least at the energy-input portion of the turbulence spectrum.

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