On the nonlinear Rossby-type wave interaction in the upper atmosphere, some numerical results

This work presents results of a numerical simulation of the nonlinear interaction between planetary Rossby-type waves. Examples considered in the work are related to several experimental studies of planetary scale day-to-day wind variations in the mesosphere and lower thermosphere during equinox and solstice. A rule for a selection of primary and secondary waves within the observed wave triads is taken following the theory of the quasi-geostrophic wave turbulence and has been checked with a nonlinear nonstationary 3D numerical model. A set of numerical experiments demonstrated that a sequence of the nonlinear interactions creates a tendency of the energy transfer to lower pseudowavenumbers. The interactions mainly generate waves with the "difference" frequency and zonal wavenumber in relation to frequencies and zonal wavenumbers of primary waves. It was demonstrated that the finite duration of the wave-wave interaction has a significant influence on amplitudes of secondary waves. This fact is not accounted for in steady-state models, which can give incorrect amplitude estimations for secondary waves in case of the short duration. (c) 2005 Elsevier Ltd. All rights reserved.