The method of digital difference filters was applied to the analysis of OH and O2 rotational temperature observations in years 2010-2018 at altitudes of 85-90 km by photometers installed in Rikubetsu (43.5N, 143.8E), Shigaraki (34.8N, 136.1E) and Sata (31.0N, 130.7E) in Japan. Seasonal variations in the monthly-average values of rotational temperature and variance of perturbations with periods of 0.7 – 11 hours, which may be associated with internal gravity waves in the mesopause region, have been studied. Seasonal variations in the relative standard deviation of rotational temperature near the mesopause have maxima in winter and summer, also minima in spring and autumn summer. The details of the changes in the rotational temperature of OH and O2 may differ. This may be due to the different heights of the luminous layers.