The impact of dehydration and extremely low HCl values in the Antarctic stratospheric vortex in mid-winter on ozone loss in spring

• Main Authors: Zhang-Liu, Yiran, Müller, Rolf, Grooß, Jens-Uwe, Robrecht, Sabine, Vogel, Bärbel, Zafar, Abdul Mannan, Lehmann, Ralph
• Format: Text
• Language: English
• Published: 2024
• Subjects: Antarc*; Antarctic; Antarctica
• Online Access: https://doi.org/10.5194/egusphere-2024-671; https://egusphere.copernicus.org/preprints/2024/egusphere-2024-671/

Simulations of Antarctic chlorine and ozone chemistry show that in the core of the Antarctic vortex (16–18 km, 85–55 hPa, 390–430 K) HCl null cycles (initiated by reactions CH 4 + Cl and CH 2 O + Cl) are effective. These HCl null cycles allow HCl mixing ratios to remain very low throughout Antarctic winter and ozone destroying chlorine (ClO x ) to remain enhanced, so that rapid ozone depletion proceeds. Sensitivity studies show that the reaction CH 3 O 2 + ClO is important for the efficacy of the HCl null cycle initiated by the reaction CH 4 + Cl and that using the current kinetic recommendations instead of earlier ones has little impact on the simulations. Dehydration in Antarctica strongly reduces ice formation and the uptake of HNO 3 from the gas phase; however the efficacy of HCl null cycles is not affected. Further, the effect of the observed very low HCl mixing ratios in Antarctic winter are considered; HCl null cycles are efficient in maintaining low HCl (and high ClO x ) throughout Antarctic winter. All simulations presented here for the core of the Antarctic vortex show extremely low minimum ozone values (below 50 ppb) in late September/early October in agreement with observations.