The interpretation of wave structures on noctilucent clouds

By observing and recording noctilucent clouds from 1967 to 1972 the presence of waves in the mesopause region was proved. From the sequence of records the wavelength and the phase velocity of the waves have been obtained, which permitted the determination of the related period of the wave motion. Assuming that internal gravity waves might be involved the site of suspected sources was predicted by using the properties of propagation of internal waves (ray tracing) and subsequently trying to identify the source regions on the contour pattern of the 300 mb surface. The results lead to the assumption that the waves are generated in the tropopause jet stream.