Simulation of planetary waves and their influence on the zonally averaged circulation in the middle atmosphere

Abstract

A linearized numerical model is used to simulate the propagation of stationary planetary waves through the stratosphere and mesosphere into the lower thermosphere. Wave forcing at the lower boundary has been specified by the perturbation of the geopotential height for January. The dependence of planetary wave structure on the zonally averaged wind is investigated through the analysis of results of simulation with different background wind distributions. The global model of stationary planetary waves has been modified to simulate traveling planetary waves, and the spectrum of resonant planetary modes has been obtained by forcing the model with a periodic perturbation of the vertical velocity near the surface. Wave-activity density, Eliassen-Palm flux, and its divergence are used as a diagnostics of wave propagation and wave-mean flow interaction. It is found that planetary waves can provide substantial acceleration of the mean flow which is comparable to that one associated with gravity wave and atmospheric tide breaking and/or saturation. Results of numerical simulation are compared with the climatological model of stationary planetary waves in the stratosphere and with the preliminary results of wind observations using WINDII instrument on the UARS.