Observations of mesospheric clouds in Latvia 1957–1983

Abstract. Until the 20th century In the 1980s, there were very few instruments for studying the upper layers of the atmosphere. Therefore, great importance was attached for observation of mesospheric clouds (MC) at an altitudes of 75–85 km., including also for amateur observations. With the development of space technologies, interest in them decreased in the second half of the 80s, but in the last decade it has grown again sharply. The reason for this is the observation of MC in places where they have not been seen before, but especially the evidence of the connection of MC appearance and parameters with the effects caused by climate change. Therefore, the study of the state and dynamics of the mesosphere and the analysis of long-term processes has again become an urgent scientific task, which, taking into account the nature of the phenomenon and the environment under study, can be effectively carried out only within the framework of international cooperation, and MC observations from the ground are an important component of this task.

Long-term visual and photographic observations of MC were carried out in the Latvian branch of the All-Union Astronomical and Geodesic Society. They started during the International Geophysical Year in 1957 and continued until 1983, that is, for 26 years. The observational materials accumulated in the archive of Latvian Astronomical society. The archive contains almost all observation logs of the mentioned period and more than 2,000 large-size photo negatives. Observations were mostly carried out according to a uniform, internationally recognized methodology, which has made it possible to obtain a unique, methodically comparable series of observations in terms of duration. The process of digitizing the observation logs has now been completed; scanning of photographs is also planned. The article summarizes information about the content of the archive materials and the information obtained from it about the observation points and the photographic technique used in them, as well as an overview of the materials obtained during the observations and their content. Reasonable importance of continuing work and performing in-depth data processing.