Antarctic Polar Stratospheric Cloud Analysis of ACE‐FTS Data From 2005 to 2023.

We present an analysis of Antarctic polar winters from 2005 to 2023 as observed by the Atmospheric Chemistry Experiment (ACE). The unique broad band infrared spectral features in ACE "residual" spectra are used to classify the spectra of polar aerosols by composition into polar stratospheric clouds (PSCs) and sulfate aerosols. The spectra of PSCs are further classified into nitric acid trihydrate, supercooled ternary solutions, supercooled nitric acid, ice‐mix, and mixtures of PSCs. A breakdown of PSC composition is presented for each year. Antarctic winter seasons with unusual compositions are: 2011, in which volcanic ash mixed with PSCs was observed from July to August; 2019, which experienced a stratospheric warming event; 2020, the PSC season following the Australian Black Summer pyrocumulonimbus event; and 2023, which had unusually large sulfate aerosols following the Honga‐Tonga Honga Ha'apai eruption of 2022. Plain Language Summary: Polar Stratospheric Clouds (PSCs) are clouds that form during polar night when temperatures in the stratosphere drop to extreme lows. These clouds play a crucial role in the annual depletion of ozone (the Antarctic "ozone hole"). We present a summary of PSC observations made from the Atmospheric Chemistry Experiment (ACE), which is a satellite‐based mission that has been operational since 2004. Key Points: Antarctic polar stratospheric cloud composition distribution during August and September observed by the Atmospheric Chemistry Experiment (ACE)Polar stratospheric cloud (PSC) composition impacted by large scale stratospheric events such as Australian Black Summer pyrocumulonimbus event and volcanic eruptionsPSC composition distribution is mostly governed by temperature [ABSTRACT FROM AUTHOR]