In January 2022, the Hunga Tonga–Hunga Ha'apai (HTHH) volcano erupted, sending massive amounts of water vapour into the atmosphere. This event had a significant impact on stratospheric and lower-mesospheric chemical composition. Two years later, stratospheric conditions were disturbed during so-called sudden stratospheric warmings. Here we simulate a novel pathway by which this water-rich eruption may have contributed to conditions during these events and consequently impacted the surface climate.

Chemistry–climate models show biases compared to surface ozone observations and thus require bias correction for impact studies and the assessment of air quality changes. We compare the performance of commonly used correction techniques for model outputs available via CMIP6. While all methods can reduce model biases, better results are obtained from more complex approaches. Thus, our study suggests broader use of these techniques in studies seeking to inform air quality management and policy.

We focus on the impact of small-scale orographic gravity waves (OGWs) above the Himalayas. The interaction of GWs with the large-scale circulation in the stratosphere is not still well understood and can have implications on climate projections. We use a chemistry-climate model to show that these strong OGW events are associated with anomalously increased upward planetary-scale waves and in turn affect the circumpolar circulation and have the potential to alter ozone variability as well.