Observations of the wavenumber 1 and 2 components of the semi-diurnal tide over Antarctica
This paper combines four years of radar wind data from Halley and Scott Base in an attempt to resolve the zonal structure of the semi-diurnal tide over Antarctica and to determine the dominant component as a function of time. If only one odd and one even wavenumber component are present then it is possible to calculate the amplitudes and phases of those using data from two stations that are similar in latitude but separated in longitude, ideally by 180. Assuming that the main components of the semi-diurnal tide at Scott Base and Halley latitudes are wavenumber 1 and 2, as has been suggested by other studies, we are able to determine the seasonal variation of both components. The wavenumber 1 component is often dominant in summer, in winter a mixture of wavenumber 1 and 2 is observed. In addition the longitude at which the maxima of the components coincide was determined and found to vary relatively little. Amplitude variations and the longitudes of maxima coincidence were used to investigate the generation mechanisms of the wavenumber 1 wave. Interaction between planetary waves with wavenumber 1 and the wavenumber 2 semi-diurnal tide was found to be a potential mechanism for the generation of the wavenumber 1 component of the tide, confirming theories and observations discussed in the literature. For periods where this explanation for the generation of the wavenumber 1 tide fails we suggest asymmetric heating through solar particle flux as an additional source.