Interannual Variability of the Atmospheric Tides over South Pole from a Decade of Meteor Wind Observations

Abstract:

The westward propagating zonal wave-number one non-migrating semidiurnal tide (SW1) and migrating diurnal tides (DW1) are dominant dynamical features present during the Austral summer over the South Pole. It has been hypothesized that the SW1 is generated by a nonlinear interaction between the zonal wave-number one stationary planetary wave in the northern hemisphere stratosphere and the zonal wave-number two migrating diurnal tide while the DW1 is believed to be a manifestation of the trapped (1-1) mode which can propagate vertically in the polar regions.

Using observations from the South Pole meteor radar system we have determined the unambiguous structure of both the DW1 and SW1 in the meridional wind field over a period of 10 years from 2001 to 2011. These observations show a clear repeatable annual structure in the amplitude and phase of the DW1 and SW1. The amplitudes grow in the spring and maximize around the summer solstice and then decay into the fall. The phase structure for both tidal components moves toward later local time from spring into summer and then earlier local times from summer towards fall, indicating a systematic and repeatable change in the vertical wavelength of these features. Over course of a decade this general trend has persisted, however there is evidence of interannual variability in both fields, but far more prominent in the SW1 field. Analysis of these waves components, their interannual variability and an interpretation of the interannual variability will be presented.