The nonlinear interaction among waves in the polar mesopause region at height from 83.4 km to 90km has been studied. The 35 h wave, semi-diurnal tides and inertial-gravity waves at period of about 8.9 h existed at almost all heights in the zonal winds and their frequencies satisfied resonance condition. The 33 h wave, semi- diurnal tides and inertial-gravity waves at period of about 19 h in the meridional winds satisfied resonance condition. By using the bispectral analysis, we found that those sets of waves were coupled each other. The maximum amplitude of semi-diurnal tide appeared just at the height where the 35 h or 33 h wave reached its minimum amplitude. The energy exchange between 35 h or 33 h waves and semi-diurnal tide was obvious. That indicates that the nonlinear wave interaction was not local only at lower atmosphere, but also at all heights in the mesopause region. The interaction leads the variation of tide amplitude temporally and spatially. The 35 h and 33 h waves may be generated by nonlinear interaction between diurnal tide and planetary waves at periods of 2-3 days at other sites or other time, and they interacted with semi-diurnal tides when they propagated to the observation site.
DownLoad: