Seasonal variations of gravity wave activity and spectra derived from sodium temperature lidar

Gravity wave measurements were carried out by a newly developed sodium temperature lidar at São José dos Campos (23°S, 46°W). The seasonal variations of gravity wave activity and spectra derived from temperature data are investigated. The total temperature perturbation and temperature vertical power spectra, Ft(m) at 2π/(8 km), 2π/(4 km), and 2π/(2 km) all show that the semiannual maxima occur near the equinoxes, which is consistent with our earlier study (Yang et al., 2006) using only sodium concentration data. The vertical structure of the mean temperature variance could be related to the vertical distribution of N2. Large nightly variability of the temperature perturbation spectral slope was also found as in other sodium concentration lidar studies. The comparison between temperature and density perturbations induced by quasi‐random waves was investigated, and the agreement was found to be good on most (∼78%) nights. Good agreement between monochromatic wave‐induced temperature perturbations and sodium concentration perturbations has also been found, and the wave parameters derived from temperature data and sodium concentration data are comparable.