Evolution of observed ozone, trace gases, and meteorological variables over Arrival Heights, Antarctica (77.8°S, 166.7°E) during the 2019 Antarctic stratospheric sudden warming

Abstract

We use ground-based spectroscopic remote sensing measurements of the stratospheric trace gases O 3 , HCl, ClO, BrO, HNO 3 , NO 2 , OClO, ClONO 2 , N 2 O and HF, along with radiosonde profiles of temperature to track the springtime development of the 2019 ozone hole over Arrival Heights (77.8 S, 166.7 E, AHTS), Antarctica, during, and after, the 2019 stratospheric sudden warming (SSW) event. Both measurements and model simulations show that the 2019 SSW caused an extraordinarily warm stratosphere within the polar vortex, resulting in record low ozone depletion over AHTS. We also contrast the evolution of the 2019 ozone hole to that in 2002, which also had a major springtime SSW event.The SSW event started around 28 th August. By $17 th September, stratospheric temperatures inside the polar vortex over AHTS were $45 K higher than the climatological average. The SSW did not cause an en masse displacement of mid-latitude air over AHTS as in the 2002 SSW event. However, the increased temperatures did cause an unusually early reduction in polar stratospheric clouds, halting the denitrification early and leading to increased gas-phase HNO 3 and record high levels of NO 2 ('renoxification'). This caused the earliest observed deactivation of chlorine, returning all active chlorine into the chlorine reservoir species, HCl and ClONO 2 . The deactivation rate into HCl remained relatively unaffected by the SSW, whilst there was a dramatic increase in ClONO 2 formation. This chlorine deactivation pathway via ClONO 2 is typical of the Arctic and atypical for the Antarctic.At AHTS, record high levels of springtime ozone were observed. The measured ozone total column did not drop below 220 DU. Record high stratospheric temperatures persisted until 7 th October over AHTS. By 22 nd October, AHTS was not beneath the polar vortex. The polar vortex break-up date on 9 th November was one of the earliest observed.

Antarctic planetary wave spectrum under different polar vortex conditions in 2019 and 2020 based on total ozone column data

“…In September 2019, a minor sudden stratospheric warming occurred over Antarctica, and this resulted in the off-pole displacement of the polar vortex, which diminished the size and duration of the OH (Figs. 1, 4; see also Yamazaki et al, 2020;Milinevsky et al, 2020;Smale et al, 2021). A significant factor in the development of the SSW was the relatively large amplitude of zonal wave-1 at high southern latitudes (Fig.…”

“…Sudden stratospheric warmings (SSWs) represent a large, short-lived dynamical change in the stratospheric polar vortex, where the circulation is disrupted by the breaking of large-scale atmospheric waves (Butler et al, 2017;Baldwin et al, 2021). SSWs occur approximately every second winter in the Arctic (Charlton & Polvani, 2007;Butler & Gerber, 2018;Baldwin et al, 2021), but they are much less frequent in the Antarctic (Butler et al, 2017;Yamazaki et al, 2020;Smale et al, 2021). The best-known Antarctic SSW is A.…”

“…This event resulted in a significant reduction in the size of the ozone hole (OH) that year (Varotsos, 2002;Allen et al, 2003) and was classed as a major warming as it satisfied the criterion of causing the reversal of the zonal wind from westerly to easterly at 10 hPa and latitude 60° (Baldwin et al, 2021). Significant minor Antarctic stratospheric warmings occurred in September 1988 (Kanzawa & Kawaguchi, 1990) and September 2019(Yamazaki et al, 2020Milinevsky et al, 2020;Smale et al, 2021;Roy et al, 2022). The warming in 2019 is particularly significant because it came close to reversing the zonal wind at 10 hPa (Rao et al, 2020;Liu et al, 2022), and the stratospheric disturbance has been shown to have significant influences on the Quasi-Biennial Oscillation (QBO) (Anstey et al, 2021) as well as the climate in parts of the Southern Hemisphere, particularly Australia (Lim et al, 2021;Klekociuk et al, 2022).…”

Retrievals of XCO2, XCH4 and XCO from portable, near-infrared Fourier transform spectrometer solar observations in Antarctica

“…To investigate this structure further we examined the isentropic modified potential vorticity (MPV) (Lait, 1994) over Arrival Heights derived from the Modern Era Retrospective-Analysis for Research and Applications reanalysis product (MERRA2) (Gelaro et al, 2017). Although not an absolute diagnostic of the position of the polar vortex relative to Arrival Heights, the MPV value will be negatively correlated with the influence of the vortex (Smale et al, 2021).…”

Retrievals of XCO2, XCH4 and XCO from portable, near-infrared Fourier transform spectrometer solar observations in Antarctica

“…To investigate this structure further, we examined the isentropic modified potential vorticity (MPV) (Lait, 1994) over Arrival Heights derived from the Modern Era Retrospective-Analysis for Research and Applications reanalysis product (MERRA2) (Gelaro et al, 2017). Although not an absolute diagnostic of the position of the polar vortex relative to Arrival Heights, the MPV value will be negatively correlated with the influence of the vortex (Smale et al, 2021). The top panel of Fig.…”