Vertical tidal wind climatology from full-diurnal-cycle temperature and Na density lidar observations at Ft. Collins, CO (41°N, 105°W)

Abstract

Vertical wind and its tidal perturbations are critical for understanding energy and momentum budgets within the Mesosphere and Lower Thermosphere. However, direct and precise observations of this tidal wind component are highly challenging due to its lowmagnitude (a few cm/s), and often smaller than the measurement uncertainty even if averaged over hours. A dynamical method to determine vertical wind tides from Na density tides was proposed and its validity tested by limited amount of data two decades ago. In this paper, we utilize the linear relationship between the perturbations of Na density and atmospheric density caused by wave perturbations to extend thismethod, and devise two new formulations for determining vertical wind tides from the Na lidar observed Na density and temperature in the mesopause region. By taking advantage of the established climatology of mean and tidal perturbations over Fort Collins, CO (41°N, 105°W), based on the data set between 2002 and 2008, we deduce diurnal and semidiurnal vertical wind tides from all three formulations. The deduced tidal amplitudes and phases are intercompared, along with the most recent, but well studied and tested, Climatological TidalModel of the Thermosphere (CTMT) based on the HoughMode Extension (HME) followed by a tidal spectrumanalysis to address the different tidal components contribution to the total tidal behavior at this midlatitude location. The comparisons show general agreement between the lidar tidal results and the model.