| Abstract: | Temperature data from SABER/TIMED and Empirical Orthogonal Function (EOF) analysis are taken to examine possible modulations of the temperature migrating diurnal tide (DW1) by latitudinal gradients of zonal mean zonal wind (\(\overline \zeta \)). The result shows that \(\overline \zeta \) increases with altitudes and displays clearly seasonal and interannual variability. In the upper mesosphere and lower thermosphere (MLT), at the latitudes between 20°N and 20°S, when \(\overline \zeta \) strengthens (weakens) at equinoxes (solstices) the DW1 amplitude increases (decreases) simultaneously. Stronger maximum in March-April equinox occurs in both \(\overline \zeta \) and the DW1 amplitude. Besides, a quasi-biennial oscillation of DW1 is also found to be synchronous with \(\overline \zeta \). The resembling spatial-temporal features suggest that \(\overline \zeta \) in the upper tropic MLT probably plays an important role in modulating semiannual, annual, and quasi-biennial oscillations in DW1 at the same latitude and altitude. In addition, \(\overline \zeta \) in the mesosphere possibly affects the propagation of DW1 and produces SAO of DW1 in the lower thermosphere. Thus, SAO of DW1 in the upper MLT may be a combined effect of \(\overline \zeta \) both in the mesosphere and in the upper MLT, which models studies should determine in the future. |
