Tidal signatures and aliasing in temperature data from slowly precessing satellites

Abstract

Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) data are used to simulate tidal patterns in satellite-borne observations of the mesosphere and lower thermosphere (MLT) region. The results are given for the measurement geometry of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, though the technique is applicable to any satellite-based instrument. TIME-GCM tides are sampled along the instrument measurement track and analyzed in terms of ascending/descending orbit node differences. Our simulations show a significant aliasing, e.g., of migrating and nonmigrating diurnal and semidiurnal components into tidal fields of observed zonal wavenumbers s′ ≥ 0. Above the mesopause, the model tides induce a 10 K bias in daily means of zonally averaged temperatures. An estimate of the tide-induced vertical displacement of air parcels is given, assuming tidal motions are adiabatic. Corresponding signatures are expected to be present in MLT observations of chemical species. Addressing tidal-sampling issues is of general interest for comparing satellite observations with models, climatologies, and other measurements. Copyright 2003 by the American Geophysical Union.