EOMF-15. Decadal Observations of Polar Mesospheric Clouds over McMurdo, Antarctica.

Abstract
The Chu Research Group was the first to report lidar observations of the Polar Mesospheric Clouds (PMCs) at McMurdo in Antarctica on 21st December 2010. This paper presents decadal variability of PMCs observed by an Fe Boltzmann Lidar at McMurdo from December 2010 through February 2020. PMCs are important tracers to study the dynamics and photochemistry of the upper atmosphere. They are also indicators of climate change as their formation relies on the presence of methane and carbon dioxide (Hervig, Mark E., et al 2015). We observed over 998 hours of PMCs, yielding the mean centroid altitude of 84.27 ± 0.04 km and the mean total backscatter coefficient of (4.79 ± 0.09) x 10-6 sr-1. The study shows an absence of solar cycle signature in averaged interannual PMC brightness over the last decade. However, the diurnal variability of brightness/altitude exhibits strong diurnal phases in the first five seasons (2010-2015) during the solar maximum period, but both diurnal and semidiurnal variations in the second five seasons (2016-2020) during the solar minimum period. This paper investigates the dependence of diurnal variability of PMCs on different phases of the solar cycle as well as atmospheric tides. We also look into the impact of cold phase of the wave-induced temperature oscillations on PMC features. Lastly, we examine the roles of temperature, water vapor and meridional wind in PMC interannual, seasonal and diurnal variability.