Short‐term variation of the s = 1 nonmigrating semidiurnal tide during the 2002 stratospheric sudden warming

Abstract

In this study, the NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME‐GCM) is used to examine short‐term changes in the global structure of the migrating and s = 1 nonmigrating semidiurnal tides in a model run approximating the 2002 Southern Hemisphere stratospheric sudden warming. The TIME‐GCM is found to resolve an s = 1 nonmigrating semidiurnal tide with latitudinal structure similar to that of prior studies and with global structure in the MLT region strongly correlated with Southern Hemisphere planetary wave 1 (PW1) wave events, prior to equinox. Comparison with a control run with no planetary wave activity, Eliassen‐Palm flux, and correlation analysis of the s = 1 semidiurnal tide structure suggest that the wave propagates from the source region in the winter hemisphere stratosphere into both the summer and winter lower thermospheres. The amplitudes of the migrating semidiurnal tide in the Southern Hemisphere are anticorrelated with the nonmigrating tide, suggesting significant energy loss due to nonmigrating tidal generation, a result not previously seen. The amplitude of the s = 1 nonmigrating semidiurnal tide from TIME‐GCM is also compared with data from the South Pole meteor radar system. While the observations show bursts of nonmigrating tidal activity correlated to PW1 activity of comparable amplitudes to the model results, these events do not always appear at the same times as those in the model. This suggests that while the processes generating the nonmigrating tide in TIME‐GCM are realistic, the TIME‐GCM run itself displays differences in time evolution compared to the observations during this time.