Nonlinear Interactions of Planetary-Scale Waves in Mesospheric Winds Observed at 52{\deg}N Latitude and Two Longitudes

Abstract

Nine years of mesospheric wind data from two meteor radars at 52{\deg}N latitude were analyzed to investigate planetary waves (PWs) and tides by estimating their zonal wavenumber through longitudinal phase differences. Our results reveal that PW normal modes (NMs) primarily drive multi-day oscillations, showing seasonal variability and statistical associations with Sudden Stratospheric Warming (SSW) events. Specifically, a significant 6-day NM emerges in April, followed by predominant 4- and 2-day NMs until June, with peaks of 2-, 4-, and 6-day NMs spanning July to October. Furthermore, our study provides the first observational verification of frequency and zonal wavenumber of over ten secondary waves from nonlinear interactions among planetary-scale waves. One notable finding is the prevalence of non-migrating components in winter 24-hour and summer 8-hour tides, attributed to these nonlinear interactions. Our findings underscore the diverse nonlinear dynamics of planetary-scale waves, triggering a variety of periodic oscillations.