Interannual variability of the diurnal tide in the low-latitude mesosphere and lower thermosphere during equinoxes: Mechanistic model interpretation of the 1992-96 HRDI measurements

We present an analysis of the interannual variability of the diurnal tide in wind and temperature observations made by the High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) in the low-latitude mesosphere and lower thermosphere from 1992-1996. Near the March equinox, the monthly HRDI diurnal tide amplitudes show strong quasi-biennial variability while the phase behavior does not reveal regular interannual variations between 80 and 110 km. Our mechanistic model-data analyses of the mean zonal wind, diurnal tide and gravity wave variances indicate that year-to-year changes in the effective tidal dissipation are a plausible mechanism for producing this strong interannual variability.