Temperature tides and waves near the mesopause from lidar observations at two latitudes

Daytime and nighttime temperature measurements covering several days enable the detection of tidal and wave perturbations in the mesopause region. This study presents two potassium lidar observations from 28 degrees N and 54 degrees N which cover more than 100 hours each. The temperature variations during this time show significant wave features, and numerical analyses allow to separate those of tidal and nontidal origin. The tidal activity under winter conditions is found to be dominated by upward propagating semidiurnal tides with amplitudes of about 10 K. Whereas a diurnal tide was also seen at 54 degrees N, it was not detectable at 28 degrees N. The data are discussed with respect to various available data sets and models. Comparisons with current numerical models show that especially the semidiurnal tide is clearly underestimated at both latitudes. The tidal activity exhibits a strong variability. This indicates nonlinear interactions with planetary waves, which have also been observed.