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

TL;DR

This study analyzes nine years of mesospheric wind data to reveal how planetary waves and tides interact nonlinearly, producing diverse oscillations and verifying secondary wave characteristics through observational data.

Contribution

It provides the first observational verification of secondary waves from nonlinear planetary wave interactions and details their influence on mesospheric tides.

Findings

Identification of seasonal variability in planetary wave normal modes

Verification of secondary wave frequency and zonal wavenumber from nonlinear interactions

Detection of non-migrating tide components linked to nonlinear wave interactions

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.