Weakening of Polar Mesosphere Winter Echo and Turbulent Energy Dissipation Rates After a Stratospheric Sudden Warming in the Southern Hemisphere in 2019

Abstract

AbstractTime variations in the polar mesosphere winter echo (PMWE) volume reflectivity and turbulent energy dissipation rates are examined during the sudden stratospheric warming (SSW) in September 2019 in the Southern Hemisphere. It was found that the frequency of PMWE occurrence decreased from early September to October, when the SSW occurred. We also found that the frequency of large turbulent energy dissipation rates (>3 × 10−4 m2s−3) was reduced compared to the average for 2016–2018. This is likely due to the modulation of gravity wave (GW) propagation by the minor SSW, resulting in less GW breaking, which is the main source of the turbulence. This suggests that the decrease in turbulence intensity is at least partly responsible for the decrease in the frequency of PMWE.