Observations of a nonmigrating component of the semidiurnal tide over Antarctica
Data obtained from the MF radars situated at Davis, Syowa and Rothera in Antarctica are used to detect a nonmigrating component of the semidiurnal tide in the mesosphere and lower thermosphere. These radars are at similar latitudes and so share a common migrating tidal component. By fitting semidiurnal tide vectors to each stations data and performing subtractions of these vectors for pairs of stations, the migrating component can be removed and the difference between the nonmigrating components revealed. Non-zero differences in the summer months (December to March) indicate the presence of a significant nonmigrating component. Modeling studies and observations at other sites suggest that it is most likely the westward propagating wavenumber 1 nonmigrating component that is contributing to the semidiurnal tide. The data presented here are found to be consistent with this hypothesis. A climatology of this nonmigrating component is presented and discussed. Comparisons with the Global Scale Wave Model suggest that latent heat release is not a significant forcing mechanism at these heights and latitudes.