Observations of small-scale billows in a strong polar mesospheric cloud (PMC) in a highly perturbed temperature/wind environment over the Poker Flat Research Range (65N, 147W) on 11-12 August 2019 by lidar, radar, and imaging

Abstract:

Poker Flat Research Range conducts an August PMC campaign each year. At 65N, twilight conditions near midnight allow high-resolution observations of PMC's directly overhead by imagers and lidars plus temperature profiles from 30-100 km, Na lidar meridional winds from 84-100 km and meteor radar winds from 82-97 km. On the night of 11-12 August 2019, a strong PMC extending over ~500 km with a backscatter coefficient of ~ 30 x 10^-10/m/sr moved in from the northeast. The was observed up by the Rayleigh lidar beam at zenith and the Na lidar beams to the north and zenith. Over 3.5 hours, the PMC layer moved from 82km altitude to 82.75km and then down to 80.5km. The temperature and wind profiles from the lidars and meteor radar shows strong altitude gradients and numerous strong gravity waves. Near the end of the event, the narrow-field imager (~3m resolution) observed a number of billows in the PMC with ~1km separation with interacting kinks and streamers. Above this at 85km, the Na lidar data indicated a strong gravity wave that produced a descending Na layer and a region of possible instability. This presentation will investigate the dynamics responsible for the formation and evolution of the billows.