Quasi-Biennial Oscillation of Short-Period Planetary Waves and Polar Night Jet in Winter Antarctica Observed in SABER and MERRA-2 and Mechanism Study With a Quasi-Geostrophic Model

Analyzing Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations from 2003 to 2018, the interannual variability of 2–5d eastward propagating planetary waves is found to correlate positively with zonal-mean zonal winds averaged over 67.5°±10°S but negatively with the quasi-biennial oscillation (QBO) index in austral winter. The composite-mean wave amplitudes are ~20% larger in QBOe than in QBOw. On statistical average, the poleward flank strengthening and the equatorward flank weakening of polar night jet (PNJ) during QBOe form a dipole-cell pattern. In contrast, only a single negative cell is seen in the Northern Hemisphere zonal-mean zonal winds (January) previously explained by the Holton-Tan theory. Such difference implies an interhemispheric asymmetry and other processes needed to explain the additional positive cell in Antarctica. Mechanistic modeling illustrates that the stronger PNJ generates eastward propagating planetary waves with larger growth rates (stronger waves) in QBOe than QBOw, explaining the QBO-like signal in the Antarctic planetary waves.