On the structure and variability of the migrating diurnal temperature tide observed by SABER

While the physical mechanisms responsible for these relationships cannot be ascertained from the obser-vations, the present results should be useful for hypothesis testing with numerical models. It is also found that the diurnal tide breaks due to convective instability in the MLT. This is reflected in its mean vertical structure, which grows as expected for a nondissipating wave below-85 km, but ceases to grow at higher altitudes.

Direct confirmation that dissipation is due to breaking is obtained from the potential temperature field, which shows frequent instances of reversed vertical gradient, particularly at the equinoxes. Breaking of the diurnal tide has a major impact on the zonal-mean temperature and zonal wind structure of the MLT at the equinoxes.