The investigators will study arctic summer phenomena, specifically noctilucent clouds (NLC) and gravity wave and tidal propagation through the middle atmosphere. The work involves an extension of the lidar capability at Sondrestrom, Greenland, into daytime operations by implementing a liquid crystal double etalon system.. The researchers will investigate the following questions: (1) What are the local time and seasonal dependencies of the behavior and characteristics of NLCs, (2) What is the impact of gravity waves and tides on the formation and lifetime of NLCs, and (3) Are there longitudinal differences in NLC observations? The daytime lidar capability will enable the gravity wave influences on NLCs to be more thoroughly analyzed, as well as the tidal influences on the basic characteristics of the clouds. Recent studies suggest that continued increases in tropospheric methane should result in an increase in mesospheric water vapor concentrations leading to more frequent NCL occurrence, particularly at lower latitudes. The gravity wave influences on this occurrence must be fully understood to assess the role of anthropogenic changes.
