Influence of semidiurnal and semimonthly lunar tides on the mesopause as observed in hydroxyl layer and noctilucent clouds characteristics

New results of research on lunar tides in the midlatitude mesopause region are presented. According to observational data on noctilucent clouds and spectrophotometric measurements of hydroxyl radiation, among the semimonthly and semidiurnal lunar tidal harmonics under consideration, the semimonthly zonal tide (13.66 days), semimonthly synodic tide (14.77 days), and semidiurnal tide (12 h 25 min) were proven to be statistically significant. The temperature oscillations in the summer hydroxyl layer and the brightness of noctilucent clouds turned out to be nearly out of phase. For the first time, we considered two possible mechanisms of the generation of the synodic semimonthly harmonic. Here, statistical analysis of the hydroxyl data shows that the nonlinear demodulation of the superposition of solar and lunar semidiurnal tidal harmonics is the most probable process.