Gravity wave spectral models and the shapes of gravity wave spectra at low vertical wavermmbers

摘要

Examples of the evolution of gravity wave spectra launched upward from the lower stratosphere are computed at unprecedented spectral resolution, as a function of altitude z, in a one-dimensional model. Empirical model energy spectra of the kind proposed by Fritts and VanZandt are used as launch spectra. The dependence of these spectra on vertical wavenumber m have a power-law behavior ms at small m, to which the total wave-energy profile Etoi(z) is sensitive. The effect on EM(z) of varying s is investigated for several cases, and the resulting Etot(z) profiles are compared with an empirical profile Eemp(z), derived by Fritts and Lu from observational studies. To the extent that Eemp(z) is realistic and the power law ms is realistic, s values around 1.5 are arguably a better choice than the value s = 1 that is often assumed faute de mieux.