Simultaneous observation of dual-site airglow imagers and a Na lidar and effect of atmospheric stability on the airglow structures

Ground-based airglow imaging has now become a popular technique for observing dynamical features in the mesopause region such as gravity waves, bores, and instabilities. The observed structures are usually regarded to exist at the height of the center of typical airglow profiles. For example, OH and OI(5577) images are usually treated as 87 km and 96 km altitudes, respectively. However, recent satellite observations such as UARS/WINDII, HRDI have clarified that there are significant variations (more than a few km) in emission profile, as well as frequent occurrence of double peak emission profiles. The dual-site airglow imagings have also suggested a significant variation of the height of structures observed in the airglow images. In this study, the structure heights in the OH airglow images were observed with two all-sky imagers at Platteville (40.2N, 104.7W) and Yucca Ridge (40.7N, 104.9W) in Colorado and atmospheric stability was determined by simultaneous Na temperature-wind lidar observations at Ft.Collins (40.6N, 105.1W). The estimated structure height was clearly affected by the existence of convectively unstable regions. Such an effect of atmospheric stability on the airglow image observations will be discussed in the paper.