大气中层顶区域波相互作用的一个观测个例

利用SOUSY VHF雷达的观测数据分析了极区中层顶83.4-91.2km范围内大气风场波动的非线性相互作用。大气风场的谱在不同高度上均有明显的潮汐分量峰值，纬向风分量中35h波、半日潮和8.9h惯必重力波构成共振相互作用对，经向风分量中33h波、半日潮和19h惯性重力波构成共振相互作用对。双谱分析表明，这些共振对在许多高度上都发生耦合，35h或33h波振幅的极小值与半日潮的极大值出现的高度几乎相同，呈现出明显的非线性相互作用在空间上不是局域的，而是存在于中层顶区域的几乎所有高度上，这种相互作用不仅导致半日潮振幅随时间的变化，也使半日潮的振幅随空间变化。35h和33h波动可能是在其他时段或其他位置通过行星波与周日潮相互作用产生的，然后传播到观测点并与半日潮发生相互作用。

A CASE STUDY OF WAVE INTERACTIONS IN THE MESOPAUSE REGION

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.