We used digital difference filters for the analysis of the spectral observations of the rotational temperature of vibrationally excited hydroxyl at altitudes 85-90 km at the Zvenigorod scientific station of IAP RAS (56° N, 37° E) in 2004-2016 and at the Geophysical observatory of ISTP SB RAS (52° N, 103° E, Tory) in 2012-2017. Seasonal and interannual changes in the mean temperature and intensity of variations with periods 0.4-5.4 h are studied. These changes may be associated with the propagation of internal gravity waves (IGWs) in the mesopause region. To filter out mesoscale variations, differences between the sequential values of the OH temperature, averaged over the intervals by duration from 10 min to 2 h, were obtained.