Possible modulation of migrating diurnal tide by latitudinal gradient of zonal wind observed by SABER/TIMED.

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. [ABSTRACT FROM AUTHOR]