Parameters of internal gravity waves based on observations of noctilucent clouds in Yakutsk

Noctilucent clouds (polar mesospheric clouds) are clusters of ice crystals 10–100 µm in size at an altitude of 80–85 km, only a few kilometers thick, illuminated by the sun's rays. A characteristic feature of noctilucent clouds is that they are observed from Earth only in relatively narrow latitudinal belts of the northern and southern hemispheres. They are a visible indicator of wave processes in the upper atmosphere. The use of modern methods of observation and data processing allows us to track their evolution and, based on these parameters, study the main dynamic characteristics of the upper atmosphere - wind speed and direction, atmospheric-gravity waves and try to establish their sources. The article presents the results of a study of the features of the parameters of internal gravity waves based on observations of noctilucent clouds. Photographic observations were carried out using digital cameras and a phone camera. Using synchronous triangulation observations with identical cameras in Yakutsk and Oktemtsy, it was possible to measure the height of noctilucent clouds. Rare cases of propagation of different types of waves and their parameters are analysed: wavelengths, speeds and directions of their propagation. A case of observation of noctilucent clouds associated with the so-called mesospheric bore is also described - a prominent wave front propagating along a waveguide channel and visually separating the glow region already involved in the wave process from the region in which oscillations have not yet arisen. It is assumed that the sources of wave disturbances are atmospheric fronts and air mass flow around mountain ranges.

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