We present analyses of data collected at Christmas Island in the mesosphere and lower thermosphere using a meteor echo detection and collection system (MEDAC) in addition to data collected in the troposphere and lower stratosphere using a clear air stratosphere/troposphere (ST) radar. These data, which provide 5 years of semicontinuous horizontal wind velocity estimates, are analyzed to determine the temporal structure of the quasi-two-day wave in the middle and lower atmosphere. Our results show the presence of strong wave activity in the middle atmosphere during late January and early February as well as a secondary maxima in June/August for each of the years we have data. However, the magnitude and duration of the wave events observed in late January and early February exhibit interannual variability. ¿ American Geophysical Union 1996