Five-years altitude statistics of noctilucent clouds based on multi-site wide-field camera survey

Abstract

The results of simultaneous measurements of noctilucent clouds (NLC) position in a number of ground-based locations are presented. Observational data of 14 bright NLC events over 5 years is used for building the altitude maps of the cloud fields using the triangulation technique updated for multi-location case. The statistical distribution of NLC altitude and its change during the summer season is considered. Mean NLC altitudes are compared with estimations by colorimetric technique based on the same data and simple radiation transfer model. This can be used to check the model and estimate the accuracy of single-camera technique of NLC altitude measurements. Clouds appear in the altitude range from 79 to 84 km, the average height of NLC is found to be 81.4 km, while the mean brightness-weighted altitude is 0.5 km below this. The brightest clouds are observed near 80 km, where the ice particles can reach the maximal size. Possible effects of the increased height of NLC during the beginning of summer (June) and maximal solar activity (2024) are noted. Results and methods are suggested for the net ground-based survey of noctilucent clouds.