Longitudinal variations of amplitudes of diurnal tides in the MLT region simulated by a general circulation model Original Research Article

Amplitudes of nonmigrating and migrating diurnal tides in the MLT region are investigated using a General Circulation Model at Kyushu University (Kyushu-GCM). It is found that the most prominent nonmigrating diurnal tidal modes at 95 km are: the eastward propagating tide with zonal wavenumber s = -3, the standing tide (s = 0), and the westward propagating tides with s = 2 and s = 3. The amplitudes of these tidal modes are somewhat smaller than 10 ms−1. These modes and migrating diurnal tide show seasonal variations. The seasonal variations of nonmigrating tidal modes are not always consistent with LIARS observations. In particular, the seasonal variation of migrating tide is different from LIARS observations. Nonmigrating diurnal modes in the model give rise to longitudinal variations of diurnal tides at this height consistent with LIARS observations.