Observational Evidence of Nonlinear Wave‐Wave Interaction Over Antarctic MLT Region

Abstract

AbstractUsing meteor radar observations over King Sejong Station (62.22°S, 58.78°W) in the Antarctic Peninsula, we investigated the wave‐wave interaction in the mesosphere and lower thermosphere (MLT) region. We analyzed hourly horizontal wind measurements at altitudes of 84–96 km from March 2016 through February 2017 and found that the MLT region is dominated by a semidiurnal tide (SDT) and the signature of planetary waves (PWs) with a period of ∼8–27 days. The PW activity was substantially intensified during the winter. The day‐to‐day variability of SDT amplitudes are estimated and the higher‐order spectral analysis of SDT amplitudes exhibits intermittent modulation of SDT at PW periods ∼8 and 27 days in the zonal winds and periods of 8 and 16 days in the meridional winds. We observed an intense episode of tidal modulation from June through September 2016, during which a set of subsidiary spectral components around the SDT were found as a result of wave‐wave interaction. Further, the bi‐spectral analysis reveals that quadratic coupling (nonlinear interaction) occurred between SDT and PWs at a band period of 8–27 days, at above 90 km. We compared the spectral powers between the secondary waves created by the nonlinear interaction between the SDT and 16‐day PWs. Further, we found that sum‐secondary waves generated by the nonlinear interaction are stronger than the difference‐secondary waves during austral winter 2016. We thus conclude that the non‐linear interaction between the tides and PWs may play a major role in the short‐term tidal variability in the MLT region during austral winter 2016.