Characteristics of Vertical Wind Fluctuations in the Lower Troposphere at Syowa Station in the Antarctic Revealed by the PANSY Radar

Abstract

Using wind data over three years from July 2012-June 2015 from the PANSY radar, an MST radar, newly installed at Syowa Station (39.59°E, 69.0°S), statistical characteristics of vertical winds and vertical momentum fluxes in the Antarctic lower troposphere are examined. Frequency spectra covering a wide frequency range from (30 d)−1 to (8 min)−1 are divided into three frequency regions obeying power laws with different scaling exponents. The transition frequencies are different between horizontal and vertical wind spectra. Vertical fluxes of horizontal momentum were estimated for two wave period ranges of 8 min–2 h and 2 h–1 d which have almost equal logarithmic scales. The momentum fluxes are larger for longer period components. There are evidences showing that the vertical wind disturbances in the lower troposphere are due to gravity waves forced by topography aligned in the north-south direction. First, the strong disturbances are observed when horizontal winds are strong near the surface. Second, zonal winds tend to almost zero around the top of the disturbances. Third, frequency spectra are large at a wide range of frequency below a critical level, as is consistent with the phase modulation of mountain waves by unsteady mean flow.