Visual and lidar observations of noctilucent clouds above Logan, Utah, at 41.7°N

Abstract

Noctilucent clouds (NLCs) were observed from a midlatitude site (Logan, Utah) on the evenings of 22 and 23 June 1999 mountain daylight time. On both nights the clouds were seen for approximately an hour by experienced observers, and they were photographed. The NLC was also observed on the second evening for approximately an hour in the zenith with the Rayleigh-scatter lidar at the Atmospheric Lidar Observatory, which is operated by the Center for Atmospheric and Space Sciences on the campus of Utah State University. These observations enabled several of the properties of the cloud to be determined. They were within the range of those observed at higher latitudes, but notably the NLC was very weak and thin. These combined visual and lidar observations unequivocally support the identification of the cloud as a noctilucent cloud. The midlatitude location (41.74°N, 111.81°W) is ∼10° equatorward of previous observations. This equatorward penetration is significant because of potential implications about global change or the global circulation.