| Abstrakt: |
Aerosol from the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcanic eruption (20.6°S) in January 2022 were not incorporated into the austral polar vortex until the following year, March 2023. Within the polar vortex in situ profiles of aerosol size spectra were completed in the austral autumns of 2019 and 2023, from McMurdo Station, Antarctica (78˚S), 30 months prior to and 15 months after the HT‐HH eruption. The measurements indicate that the HT‐HH impact on aerosol size was primarily confined to particles with diameters >0.5 μm leading to differences in aerosol mass, surface area, and extinction from factors of 2–4 at the volcanic layer's peak below 20 km, increasing to ratios of 5–10 above 20 km. Effective radius, with radiative and microphysical implications, increased from ∼0.2 to ∼0.3 μm. An Earth system model with a modal aerosol package compares favorably with the in situ measurements of the HT‐HH aerosol impact. Plain Language Summary: In austal autumn of 2019 and 2023 balloon‐borne measurements of aerosol size distributions were completed above McMurdo Station, Antarctica (78˚S, 167˚E). Size spectra were measured for particles between 0.01 and 16 μm from the surface to over 30 km. Between these two sets of measurements the Hunga Tonga‐Hunga Ha'apai (HT‐HH) volcano (20.6°S) started an eruptive phase culminating with a massive underwater explosion on 15 January 2022. Due to the timing of the eruption, the HT‐HH volcanic aerosol were not incorporated into the austral polar vortex until 2023, which formed about a month before the 2023 aerosol measurements were completed. The 2019 measurements were in a volcanically quiescent period and capture the background stratospheric aerosol. The two sets of measurements are used to characterize the impact of HT‐HH on stratospheric aerosol within the austral polar vortex, particularly on quantities important for assessing the volcanic impact on climate and heterogeneous chemistry: aerosol mass, surface area, and light extinction. Such quantities were observed to increase by factors of 2–4 below, and 5–10 above, 20 km after the eruption. An Earth System Model with an aerosol package compared favorably wih the measurements. Polar ozone loss in 2023 was, however, not impacted significantly. Key Points: Austral polar vortex aerosol concentrations from Hunga Tonga increased, for particles >0.5 μm, by factors of 2–5 below, >10 above, 18 kmConcomittant increases in SO4 mass, surface area, and near IR extinction were by factors of 2–4 below, and 5–10 above, 18 kmEffective radius, with radiative and microphysical implications, increased from ∼0.2 to ∼0.3 μm at the peak of the layer [ABSTRACT FROM AUTHOR] |
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