## Abstract

The author presents an alternative to proposed mechanisms explaining horizontal wind gravity wave vertical wavenumber spectra by assuming that the damping effects of molecular viscosity, turbulence, and off-resonance wave-wave interactions can be characterized in terms of a scale-independent diffusivity (D) which increases with altitude. A wave of intrinsic frequency ω and vertical wave number m is assumed to be completely damped when the effective vertical velocity of momentum diffusion (mD) exceeds the vertical phase velocity of the wave (ω/m). Only waves satisfying mD < ω/m, or equivalently m^{2}D < ω and m < ω/D)^{1/2} are permitted to grow in amplitude as they propagate upward in the atmosphere. If the gravity wave temporal spectrum of horizontal winds varies as ω^{-p}, we show that the vertical wave number spectrum must vary as m^{-2p+1} and the zonal (or meridional) wave number spectrum must vary as k^{-(2p+1)/3}. The spectra are proportioinal to ω^{-p}, m^{-3} and k^{-(3p-1)/(p+1)}. Because the joint (m, ω) intrinsic spectra for both scale-independent and scale-dependent diffusive filtering are not separable, the theory predicts that the m spectra of vertical winds are proportional to m^{5-2p} for scale-independent diffusion and m(^{7-3p)/(p-1)} for scale-dependent diffusion. -from Author

Original language | English (US) |
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Pages (from-to) | 20,601-20,622 |

Journal | Journal of Geophysical Research |

Volume | 99 |

Issue number | D10 |

State | Published - 1994 |

Externally published | Yes |

## ASJC Scopus subject areas

- Geophysics
- Forestry
- Oceanography
- Aquatic Science
- Ecology
- Water Science and Technology
- Soil Science
- Geochemistry and Petrology
- Earth-Surface Processes
- Atmospheric Science
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science
- Palaeontology