Nonmigrating Diurnal Tide DE3 Responses to the 2003/2004 Sudden Stratospheric Warming

Atmospheric tides can be divided into migrating tides, which propagate westward with the apparent motion of the Sun, and nonmigrating tides, which deviate from this sun-synchronous propagation. Among the latter, the nonmigrating diurnal tide DE3 is a major component of variability in the mesosphere and lower thermosphere (MLT), yet its event-scale response to stratospheric sudden warmings remains less well constrained, especially in terms of daily resolved observational evidence and its connection to the background propagation environment. Here, we analyze DE3 variations during the 2003/2004 Northern Hemisphere winter sudden stratospheric warming (SSW) using the daily DE3 product derived from TIMED/SABER observations and Hough mode decomposition. Results show an overall suppression of DE3 following the onset of SSW: In the vicinity of the equator, the amplitude of DE3 remained at significantly low levels during the warming period, and the 90–108 km mean-amplitude at representative latitudes indicates a reduced post-SSW amplitude. The warming/nonwarming comparison reveals clear suppression of DE3 near the equator. The multiyear comparison further shows that the DE3 amplitude during the post-warming stage is significantly lower than that in the control years. Hough-mode projections indicate that DE3 is mainly contributed by the low-order modes, with the leading symmetric (3,3) mode showing selective and delayed suppression. These features are consistent with a possible dynamical pathway in which SSW-related changes in low-latitude zonal-mean zonal wind and its meridional shear modify the equatorial propagation environment, which may contribute to the weakening of the equatorially concentrated leading symmetric (3,3) mode and the overall suppression of DE3.