Meteor radar observations of vertically propagatinglow-frequency inertia-gravity waves nearthe southern polar mesopause region

Abstract

Vertically propagating low-frequency inertia-gravity waves (IGWs) are retrieved from meteor radar winds observed at King Sejong Station (KSS: 62.22S, 58.78W), Antarctica. IGW horizontal wind components extracted from band-pass filtering and reconstructed in regular time-height bins demonstrate the persistent occurrence of IGWs, the downward progression of their phases and the counterclockwise rotation of horizontal wind vectors (i.e., upward energy propagation) near the mesopause region throughout the whole year 2014. Stokes parameters and rotary spectra computed from the hodographs of IGW horizontal wind components reveal that the intrinsic frequencies of the upward propagating IGWs are |f|-3|f| with seasonal variations of the relative predominance between |f|-2|f| and 2|f|-3|f|, where f is the Coriolis parameter at KSS. The vertical wavelengths of observed IGWs roughly range from 14 km to more than 20 km, which is consistent with previous observational studies on the mesospheric IGWs over Antarctica. Hodograph analysis indicates that the N-S propagation is dominant in austral summer, while the NE-SW propagation is pronounced in austral winter. The propagation direction is discussed in related to the generation of IGWs due to dynamic imbalances occurring in the tropospheric and stratospheric jet flow systems. Ray-tracing results indicate that the N-S propagation in summer may be due to the jet-flow systems roughly north of KSS and the NE-SW propagation in winter may be either the SW propagation from the jet-flow systems northeast of KSS or the NE propagation (around the South pole) from the south of Australia and Southern Indian Ocean.