19 Jan 2024
 | 19 Jan 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Investigating long-term changes in polar stratospheric clouds above Antarctica: A temperature-based approach using spaceborne lidar detections

Mathilde Leroux and Vincent Noel

Abstract. Polar stratospheric clouds play a significant role in the seasonal thinning of the ozone layer by facilitating the activation of stable chlorine and bromine reservoirs into reactive radicals, as well as prolonging the ozone depletion by removing HNO3 and H2O of the stratosphere by sedimentation. In a context of climate change, the cooling of the lower polar stratosphere could enhance the PSC formation and by consequence cause more ozone depletion. There is thus a need to document the evolution of the PSC cover to better understand its impact on the ozone layer. In this article we present a statistical model based on the analysis of the CALIPSO PSC product from 2006 to 2020. The model predicts the daily regionally-averaged PSC density by pressure level derived from stratospheric temperatures. Applying our model to stratospheric temperatures from the CALIPSO PSC product over the 2006–2020 period shows it is robust in the stratosphere between 10 and 150 hPa, reproducing well PSC variations over daily timescales and seasonal differences (2006–2020). The model reproduces well the PSC seasonal progression, even during disruptive events like stratospheric sudden warmings, except for years characterized by volcanic eruptions. We apply our model to gridded stratospheric temperatures from reanalyses over the complete south pole domain to evaluate changes in PSC seasons over the 1980–2021 period. We find two distinct periods in the evolution of the PSC season duration. Between 1980 and 2000, the PSC season increased by 15 days at 10–20 hPa with an increasing lengthening as we descend in altitudes to reach 30 days at 100–150 hPa. This lengthening is in possible relation with major eruptions occurring over this period. After 2000, a temporary drop mostly visible at high (10–20 hPa) and lower altitude (100–150 hPa) is followed by a progressive increase in PSC season duration. Over the 1980–2020 period, the PSC season increased by 20 days between 30–100 hPa. These changes are altitude-dependent and statistically significant. We discuss the impact of non-temperature stratospheric changes on the variations of PSC seasons.

Mathilde Leroux and Vincent Noel

Status: open (until 01 Mar 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-131', Anonymous Referee #1, 05 Feb 2024 reply
  • RC2: 'Comment on egusphere-2024-131', Anonymous Referee #2, 09 Feb 2024 reply
Mathilde Leroux and Vincent Noel
Mathilde Leroux and Vincent Noel


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Short summary
This study investigate the long-term changes in the polar stratospheric cloud (PSC) season from 1980 to 2021 above Antarctica. We analyzed spaceborne lidar observations from 2006 to 2020 to build a statistical temperature-based model. We applied our model to gridded reanalysis temperatures, leading to an integrated view of PSC occurrence that is free from sampling issues, allowing us to document the past evolution of the PSC season. We find that PSC season gets longer over the 1980–2000 period.