Comment on acp-2022-247

Abstract

A record-breaking stratospheric ozone loss was observed over the Arctic and Antarctica in 2020. Strong ozone depletion occurred over Antarctica in 2021 as well. The ozone holes developed in smoke-polluted air. In this article, the impact of Siberian and Australian wildfire smoke (dominated by organic aerosol) on the extraordinarily strong ozone reduction is discussed. The study is based on aerosol lidar observations in the North Pole region (October 2019–May 2020) and over Punta Arenas in southern Chile at 53.2° S (January 2020–November 2021) as well as on respective NDACC (Network for the Detection of Atmospheric Composition Change) ozone profile observations in the Arctic (Ny-Alesund) and Antarctica (Neumayer and South Pole stations) in 2020 and 2021. We present a conceptual approach how the smoke may have influenced the formation of polar stratospheric clouds (PSCs) which are of key importance in the ozone-depleting processes. The main results are as follows: (a) The direct impact of wildfires smoke (below the PSC height range, at 9–12 km height) on additional ozone reduction seems to be similar to the impact of the well-known volcanic sulfate aerosol effects. Smoke particle surface area (SA) concentration of 5–7 μm2 cm-3 (Antarctica, spring 2021) and 6–10 μm2 cm-3 (Arctic, spring 2020) was correlated with a smoke-related additional ozone loss in terms of ozone partial pressure of 0.4–1.2 mPa (30–50 % of the total ozone loss, Antarctica) and 2–3.5 mPa (again 30–50 %, Arctic) at heights from 9–12 km. (b) Within PSCs (14–23 km height range), we found indications that smoke was able to slightly increase the PSC particle number and surface area concentration. In particular, a smoke-related additional ozone loss of 1–1.5 mPa (10–20 % contribution to the total ozone loss) was observed in the central 15–20 km PSC height range over Antarctica in September–October 2020 and 2021, however, independent of the strength of the smoke pollution, i.e., for smoke particle number concentrations ranging from 10 to 100 cm-3 (a factor of 3–10 above the stratospheric aerosol background level). A similar amount of 1–1.5 mPa smoke-related ozone loss was estimated for the PSC height range over the Arctic in spring 2020. Satellite observations indicated an additional mean column ozone loss (deviation from the long-term mean) of 26–30 Dobson units (9–10 %, September 2020, 2021) and 52–57 Dobson units (17–20 %, October 2020, 2021) in the smoke-polluted latitudinal Antarctic belt from 70°–80° S.