Impact of QBO and ENSO in the southern hemisphere polar middle atmosphere

Both quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO) can strongly influence the middle atmosphere circulations and tracer gases (e.g. ozone and water vapor). In this study, we investigate the influence of QBO and ENSO in the early summer southern hemisphere (SH) polar middle atmosphere. Analyses use the observed satellite dataset from the Microwave Limb Sounder (MLS) between 2004 and 2018, simulations from the specified-dynamics Whole Atmospheric Community Climate Model version 4 (SD-WACCM4) between 1979 and 2015, and the European Centre for Medium‐Range Weather Forecasting (ECMWF) Reanalysis (ERA‐Interim) between 1979 and 2018. We find that theQBO and ENSO could dramatically impact the SH planetary wave (PW) propagation in November and lead to anomalous SH stratosphere Brewer-Dobson (BD) circulation, polar temperature and ozone.During QBO easterly phases and El Niño events in November, the SH stratospheric polar vortex breaks much earlier than other years, leading to warmer polar stratosphere temperature and anomalous ozone density. The decreased stratosphere westerly zonal winds in the SH high latitudes further allow more eastward GWs to propagate into the SH mesosphere, leading to the enhanced upwelling and cooling in the SH summer polar mesosphere.