Chemical ozone loss and chlorine activation in the Antarctic winters 2013–2020

Abstract. Since its discovery in 1985, the formation of ozone holes in the Antarctic and the resulting ultra-violet (UV) radiation reaching the planet's surface has been a source of major concern. The annual formation of ozone hole in the austral springs has regional and global climate implications. Ozone depletion episodes can change precipitation, temperature, and atmospheric circulation patterns, affecting the surface climate primarily in the southern hemisphere (SH). Therefore, the study of ozone loss variability is important to assess its consequential effects on the climate and public health. Our study examines and quantifies the ozone loss and its cycle for the past 8 years in the Antarctic using satellite measurements (Microwave Limb Sounder on Aura). We observe the highest ozone loss (3.8–4.0 ppmv) in spring 2020 followed by 2016. The high chlorine activation (2.3 ppbv), stable polar vortex and extensive areas of polar stratospheric clouds (PSCs) (12.6 Million Km²) favored the large ozone loss in 2000. The spring of 2019 also witnessed a moderately high ozone loss, although the year was marked by a rare minor warming in mid-September. Relatively smaller ozone loss (2.4–2.5 ppmv) was present in 2017 and 2015. It was mainly due to reduced chlorine activation and relatively higher temperature in these winters. Additionally, the chlorine activation in 2015 (1.95 ppbv) was the lowest and the wave forcing from the lower latitudes was very high in 2017 (up to -60 Kms^-1). The analysis shows significant interannual variability in the Antarctic ozone as for the immediate previous decade. The study helps to understand the role of the dynamics and chemistry in the inter-annual variability of ozone depletion for the years.