Cross comparison of TIDI winds with meteor RADAR winds and assessment of the accuracies depending on local time and geographical latitude

Abstract

The mesosphere and lower thermosphere (MLT) is a highly variable region. This variability is driven by atmospheric waves covering various temporal and spatial scales from minutes to days and from kilometers to the planetary dimension. Furthermore, this altitude region forms the transition between the neutral forcing from below due to dynamical, chemical, radiative process but is also affected by forcings from above closely related to the ionized component and solar variations. Atmospheric tides are global-scale waves in temperature, winds, and density with periods that are harmonics of a solar day. By transporting energy and momentum from the troposphere and stratosphere to upper altitudes the upward propagation of atmospheric tides is one of the key processes at all latitudes that alters the state of the ionospheric-thermospheric system TIMED Doppler Interferometer (TIDI) is a Fabry-Perot interferometer designed to measure winds, temperatures, and constituents in the mesosphere and thermosphere. TIDI achieves day and night coverage of neutral wind and temperature measurements throughout the MLT by performing limb scans through the terrestrial airglow layers along the satellite orbit. Four views in four orthogonal directions provide the measurements necessary to construct the horizontally resolved vector winds as a function of altitude within the MLT region along two parallel tracks, one on either side of the spacecraft. The orbit precession rate of TIMED requires that tidal parameters obtained using a Fourier method be accumulated over 60 days. The tidal decomposition is performed by applying a global harmonic fit including their spatial wavenumbers, which permits to separate migrating and non-migrating tidal modes for the entire globe. We establish a tidal climatology, compare our results to existing climatologies derived from local meteor radar observations and assess this comparison depending on local time and geographical latitude.