A statistical analysis of the energy dissipation rate estimated from the PMWE spectral width in the Antarctic
(Left) The local time dependence of the monthly mean of ε (color) and SZA (contour) for z=70–75 km. (Right) A histogram of the logarithm of ε for SZA=90°-95° and z=70–75 km.要旨
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 four 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 3×10-5 to 3×10-1 m2s-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.