The method of digital difference filters is applied to the data analysis of the observations of rotational temperature of hydroxyl nightglow at altitudes 85 – 90 km with the airglow temperature photometers in Rikubetsu (43.5N, 143.8E) Shigaraki (34.8N, 136.1E) and Sata (31.0N, 130.7E) Japan in years 2010 – 2018. Seasonal changes in the monthly-average values and standard deviations of variations with the periods 0.7 – 11 h are studied, which can be connected with internal gravity waves in the mesopause region. Monthly-averaged temperature near the mesopause has a maximum in winter and a minimum in June. Multi-year trends correspond to strengthening the mesoscale disturbance intensity near the mesopause. Details of interannual changes and multi-year trends of the rotational temperature OH emission intensity can be different. This is connected with different heights of the emission layers.