Tides over Antarctica: Comparison of Whole Atmosphere Model (WAM) Simulations with Ground-Based Observations

Abstract:

Ground-based radar and optical observations of winds and temperature reveal a rich and variable spectrum of tidal oscillations in the mesosphere/lower thermosphere (MLT) over Antarctica, including the South Pole. Large-scale perturbations over the pole may formally be represented only with zonal wavenumbers 0 or 1. Only the latter may support winds and the only migrating tide that can exist over the pole is the diurnal westward DW1. Other tidal periods projecting on the permitted wavenumbers inevitably correspond to nonmigrating waves such as the well documented semidiurnal westward SW1. Migrating tides make a noticeable contribution over the edges of the continent posing an identification problem for stations on the ground. Free-running WAM simulations show good agreement in amplitude, phase, seasonal and day-to-day variability of prominent tides with observations by some ground-based instruments but less so with others. Because the model dynamics is self-consistent, this implies that estimates of tidal variations of different parameters, e.g., temperature and winds, or from different instruments cannot be all correct. More cross-validation and detailed analyses of estimate errors and biases are needed.