Suggested components of a GW parameterization design that includes the major sources and modifying influences: 1. individual source spectra in amplitude, scales & phase speeds or frequency & wavenumber (one size does not fit all!) 2. composite source spectrum (if appropriate) 3. proper accounting for competing processes causing spectral evolution (the “source” spectrum surely evolves significantly with altitude and time) 4. an “action” spectrum that forces the atmosphere at greater altitudes (and may differ greatly from a simple “filtered” source spectrum)

Major components contributing to spectral evolution likely include: 1.refraction and filtering (linear theory and RT are good guides) 2. amplitude variations with z and c g (linear theory good ONLY IF vertical propagation is fast) 3. GW “breaking” and turbulence (linear theory is poor, nonlinear modeling “guidance” required) 4. accounting for effects of wave-wave interactions seems essential at higher altitudes and for slow vertical propagation

GW source spectrum topographyconvectionwind shearWMD refraction filtering growth with z, c g GW “breaking” & turbulence wave-wave interactions GW “action” spectrum