Inertia-gravity waves revealed in radiosonde data at Jang Bogo Station, Antarctica (74o37'S, 164o13'E). Part I: Characteristics, energy, and momentum flux

Abstract

Characteristics of inertia-gravity waves (IGWs) at high-latitude in Antarctica are investigated using radiosondes launched daily at Jang Bogo Station (74o37'S, 164o13'E), a new Antarctic station that has been operating since 2014, in the troposphere (z = 2？7 km) and lower stratosphere (z = 15？22 km) for 25 months (December 2014？December 2016). The vertical propagation of IGWs exhibits strong seasonal variations in the stratosphere, with an enhancement (reduction) in downward (upward)-propagating IGWs from May to mid-October. In the troposphere, both upward and downward-propagating IGWs have similar occurrence rates without seasonal variations. The intrinsic phase velocity of IGWs mostly direct to the west (isotropic), while the ground-relative phase and group velocities are dominant in the east and southeast (northeast), respectively, in the stratosphere (troposphere). The intrinsic frequency, vertical wavelength, and horizontal wavelength of IGWs averaged in the troposphere (stratosphere) are 3.57 f (1.93 f) (where f is the Coriolis parameter), 1.48 (1.48) km, and 63.06 (221.81) km, respectively. The wave energy in the stratosphere has clear seasonal variations with large values in autumn and spring, while that in the troposphere is smaller without obvious seasonal variations. Zonal and meridional momentum flux (MF) averaged in the stratosphere (troposphere) are -0.008 (-0.0018) m2 s-2 and -0.0005 (0.001) m2 s-2, respectively. The MFs of downward-propagating IGWs in the stratosphere is mostly positive in both zonal and meridional directions, whereas the directional preference is not obvious in the troposphere. In Part II, sources of the observed IGWs in the troposphere and stratosphere will be examined.