Observations of the breakdown of an atmospheric gravity wave near the coldsummer 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 inst ability, of an atmospheric gravity wave. A. second set of simultaneous airg low/lidar observations, showing wave breakdown, has been obtained over Kuhl ungsborn, 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 o ccurrence of NLCs. This new set of data shows that the first observations w ere not a unique event, and give credence to the suggestion that some of th e small scale structure seen in NLC displays may be due to wave breakdown.