Inertia­Gravity Waves Revealed in Radiosonde Data at Jang Bogo Station, Antarctica (74°37′S, 164°13′E): 2. Potential Sources and Their Relation to Inertia­Gravity Waves

Abstract

Potential sources of inertia-gravity waves (IGWs) in the lower stratosphere (z = 15-22 km) at Jang Bogo Station, Antarctica (74 degrees 37 ' S, 164 degrees 13 ' E) are investigated using 3-year (December 2014 to November 2017) radiosonde data, including the 25-month result (December 2014 to December 2016) analyzed in Yoo et al. (2018, https://doi.org/10.1029/2018JD029164, Part 1). For this investigation, three-dimensional backward ray tracing calculations are conducted using the Gravity wave Regional Or Global RAy Tracer. Among 248 IGWs, 112, 68, and 68 waves are generated in the troposphere (z < 8 km), tropopause (z = 8-15 km), and lower stratosphere (z = 15-18.5 km), respectively. These waves mainly propagate from the northwestern and southwestern regions of Jang Bogo Station dominated by the prevailing westerlies between the upper troposphere and lower stratosphere. Potential sources of IGWs are categorized into orography, fronts, convection, and the flow imbalance including the upper-tropospheric jet stream. In the troposphere, relatively large numbers of waves are associated with fronts (37) and orography (35) compared with convection (28). In the tropopause (stratosphere), 36 (42) waves, including 11 cases associated with the upper-tropospheric jet stream, are excited by the flow imbalance. Waves related to the flow imbalance are characterized by low intrinsic frequency (1-2f), short vertical wavelength (1-2 km), and longer horizontal wavelength (50-1000 km), whereas the waves induced by the tropospheric sources have wider ranges of intrinsic frequency (1-20f) and vertical wavelengths (1-15 km) with relatively shorter horizontal wavelengths (less than 500 km).