Analysis of a Decade of PMC Observations by Fe Boltzmann Lidar at McMurdo, Antarctica

Polar Mesospheric Clouds or PMCs serve as sensitive tracers for observing and studying the dynamics of the MLT region. They act as a natural laboratory for various middle and upper atmospheric phenomena and help in detecting long term climate change. Since last decade, various instruments and simulation models have identified and analyzed the properties of polar mesospheric clouds. This paper reports the findings of PMCs observed from an Fe Boltzmann lidar stationed at McMurdo in Antarctica for the last 10 years. The lidar observed over 1002 hours of PMCs, resulting in an occurrence frequency of 31.13%. Through analyzing 10 seasons of summer in Antarctica, we focus on characterizing inter annual, seasonal and diurnal variations of PMCs. The paper reports a negative correlation between seasonal centroid altitude and seasonal brightness with a confidence level of 97%. The mean centroid altitude is 84.76 ± 0.05 km and the mean total backscatter coefficient is (4.03 ± 0.08) x 10^-6 sr^-1.The mean centroid altitude of PMCs observed at McMurdo supports the previous theory of increase in PMC centroid altitude with latitude increase.

We look into interrelation of PMC features with mesospheric and stratospheric temperature and water vapor data obtained from MLS. Since satellite observations have shown an absence of solar cycle in relation with PMCs, one of the goals of this paper is to investigate the solar cycle signature or lack of it from the perspective of ground based lidar observations from 2010 - 2020. The paper answers the question - Does Lyman alpha irradiance and solar flux have a significant impact on PMCs, considering the current solar cycle is the smallest one since 1947? It also examines the plausible association of PMC features with various atmospheric phenomena such as - inter-hemispheric coupling, gravity waves, planetary waves, QBO signatures, wind reversal, polar vortex and teleconnection.