A Statistical Analysis of the Energy Dissipation Rate Estimated From the PMWE Spectral Width in the Antarctic

Abstract

The radar volume reflectivity and turbulent kinetic energy dissipation rate in the Antarctic mesosphere were estimated from the polar mesosphere winter echoes (PMWE) recorded using a vertical beam of the PANSY radar, a Mesosphere‐Stratosphere‐Troposphere radar at Syowa Station (69°S, 40°E), over a period of 4 years. The observed radar volume reflectivity exhibits a lognormal distribution in the range of 2 × 10−18 to 5 × 10−15 m−1 for a height region of 55–82 km. The turbulent energy dissipation rate estimated from the spectral widths of the PMWE ranges from 10−4 to 100 m2 s−3. From monthly histograms of the turbulent energy dissipation rate for a fixed solar zenith angle (SZA) and height, it was found that the summer‐to‐winter transition of the turbulent energy dissipation rate occurs in March, while the winter‐to‐summer transition occurs in September. This seasonal variation agrees well with that of gravity wave activity, suggesting that the turbulence in the mesosphere is likely caused by gravity wave breaking.

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

“…The height range of 65-75 km, where the PMWE is most frequently observed, is the focus. fact that PMWE at night and at high altitudes can only be detected when  is large (Kohma et al, 2020). In Period B, the frequency for  greater than 3 × 10 −4 m 2 s −3 is smaller in 2019 than the average for 2016-2018, while there is little difference in the frequency for  smaller than 3 × 10 −4 m 2 s −3 .…”

“…The detailed procedure for calculating the turbulent velocity variance is described by Kohma et al. (2019; 2020), where beam broadening was subtracted by an algorithm developed by Nishimura et al. (2020).…”

“…The radar parameters for this period are described in Kohma et al. (2020). Details of the PANSY radar system are given in K. Sato et al.…”

“…In the present study, we used observation data from the full radar system for August through October in the four-year period of 2016-2019. The radar parameters for this period are described in Kohma et al (2020). Details of the PANSY radar system are given in K. Sato et al (2014).…”

“…The calculation of the radar volume reflectivity  was performed following K. Sato et al (2014Sato et al ( , 2017. The minimum  detectable by the PANSY radar is on the order of 10 −18 m −1 (Kohma et al, 2020). The turbulence parameters were derived from the spectral widths of the PMWE following Hocking (1983) and T. Sato & Woodman (1982).…”