Seasonal and Interannual Variations of Global Tides of Neutral Winds in the Mesosphere and Lower Thermosphere

The seasonal and interannual variations of global tides of neutral winds in the mesosphere and lower thermosphere (MLT) are investigated based on the neutral horizontal wind data measured by TIMED Doppler interferometer (TIDI). The particular focus is on how the seasonal variation of tidal amplitude varies in response to solar cycle (SC) and to the quasi-biennial oscillation in winds in the lower stratosphere (SQBO). We find that the responses of seasonal variations of tides to SQBO and SC are comparable in magnitude to those of their corresponding annual means. Further, we show that the response patterns of seasonal variations of tides to SQBO and SC are not always similar to those of their corresponding annual means, which indicates that the tidal responses differ at different times of the year. In addition, we reveal that migrating tides show strong terannual oscillations (TAO) especially in meridional wind, whereas nonmigrating tides do not show obvious TAO.