Isentropic advection by gravity waves: Quasi‐universal M −3 vertical wavenumber spectra near the onset of instability

A two‐dimensional model was used to advect air parcels under the influence of a linear superposition of hydrostatic gravity waves. As wave amplitudes increased, vertically profiled wave perturbations became nonsinusoidal, producing increased spectral power at large wavenumbers M . At saturation amplitudes just before onset of convective instabilities, these “tail spectra” assumed universal M −3 shapes, similar to observed spectra in the atmosphere and oceans.