Planetary scale and tidal perturbations in mesospheric temperature observed by WINDII

Abstract

WINDII, the Wind Imaging Interferometer on the Upper Atmospheric Research Satellite measures winds and emission rates from selected excited metastable species. Here we report on measurements of the atmospheric Rayleigh scattering from the O(1S) background filter at 553 nm wavelength used to derive temperature profiles in the upper mesosphere from 70 km to 95 km, for solstice periods from December 1992/93 and January 1993/94. The data are first zonally averaged and then combined in local time over about one month. Based on these temperatures, an analysis of planetary wave structures and tidal perturbations employing least-mean-square (LMS) fits to the data has been conducted and the results are presented. The planetary wave structures observed were well described with a quasi two-day wave (QTDW). Amplitudes of 14 K and 10 K at 85 km height for downleg (descending) and upleg (ascending) sampling respectively at latitudes from 20°S to 40°S were found to be in good agreement with QTDW temperature results from the MLS/UARS experiment assuming a vertical amplitude structure of the type described by the HRDI/UARS mesospheric wind observations. It is shown that the diurnal tide amplitudes estimated from latitudes from 25°N to 35°S using the LMS fit maximize at the equator with an amplitude of about 6 K and decrease toward tropical latitudes, consistent with the classical tidal theory and predictions from the TIME-GCM model.