Observations of the breakdown of an atmospheric gravity wave near the cold summer mesopause at 54N

Recently, it was shown from a single set of air-glow/lidar observations in Urbana, Illinois (40N) that some small-scale wave-like structure seen in OH airglow images can be associated with the breakdown, via a convective instability, of an atmospheric gravity wave. A. second set of simultaneous airglow/lidar observations, showing wave breakdown, has been obtained over Kuhlungsborn, Germany (54N) during a period when noctilucent clouds (NLCs) were also observed. This showed that the wave breakdown process can occur under the same cold, low altitude summer mesopause conditions that support the occurrence of NLCs. This new set of data shows that the first observations were not a unique event, and give credence to the suggestion that some of the small scale structure seen in NLC displays may be due to wave breakdown.