The longitudinal variability of the semidiurnal tide in the Antarctic upper mesosphere is investigated by comparison of observations from two radars at approximately opposite sides of Antarctica. Under the assumption that the tide is composed of an S = 2 (migrating) and S = 1 (westward-propagating, non-migrating) component only, the relative phases of the components are shown to vary with season such that the waves are typically in constructive interference during the winter (summer) months at longitudes around 0 degrees E (180 degrees E). We show that this has profound effects on the seasonal behaviour of the semidiurnal tide around 78 degrees S dependent on the longitude, and that no single-station observations at this latitude can be considered representative of a "zonal mean". The superposition of these two waves is used to interpret differences in previously-published ground-based climatologies of the tide. Citation: Hibbins, R. E., O. J. Marsh, A. J. McDonald, and M. J. Jarvis (2010), A new perspective on the longitudinal variability of the semidiurnal tide, Geophys. Res. Lett., 37, L14804, doi:10.1029/2010GL044015
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