Preprints
https://doi.org/10.5194/egusphere-2024-1849
https://doi.org/10.5194/egusphere-2024-1849
08 Jul 2024
 | 08 Jul 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Australian Bushfire Emissions Result in Enhanced Polar Stratospheric Ice Clouds

Srinivasan Prasanth, Narayana Sarma Anand, Kudilil Sunilkumar, Subin Jose, Kenath Arun, Sreedharan K. Satheesh, and Krishnaswamy K. Moorthy

Abstract. Extreme bushfire events amplify climate change by emitting greenhouse gases and destroying carbon sinks while causing economic damage through property destruction and even fatalities. One such bushfire occurred in Australia during 2019/2020, injecting large amounts of aerosols and gases into the stratosphere and depleting the ozone layer. While previous studies focused on the drivers behind ozone depletion, the bushfire impact on the polar stratospheric clouds (PSC), a paramount factor in ozone depletion, has not been extensively investigated so far. This study focuses on the effects of bushfire aerosols on the dynamics and stratospheric chemistry related to PSC formation and its pathways. An analysis from Aura's microwave limb sounder revealed enhanced hydrolysis of dinitrogen pentoxide significantly increased nitric acid (HNO3) in the high-latitude lower stratosphere in early 2020. Using a novel methodology which retrieves formation pathways of PSCs from spaceborne lidar observations, we found that the enhanced HNO3 condensed on bushfire aerosols, forming 82 % of Liquid Nitric Acid Trihydrate (LNAT), which rapidly converted to 77 % of ice, resulting in an anomalous high areal coverage of ice PSCs. This highlights the primary formation pathways of ice and LNAT and possibly helps us to simulate the PSC formation and denitrification process better in climate models. As tropospheric warming is anticipated to increase the frequency of extreme wildfire events and stratospheric cooling is expected to expand the PSC areal coverage, these findings will contribute significantly to a deeper understanding of the impacts of extreme wildfire events on stratospheric chemistry and PSC dynamics.

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Srinivasan Prasanth, Narayana Sarma Anand, Kudilil Sunilkumar, Subin Jose, Kenath Arun, Sreedharan K. Satheesh, and Krishnaswamy K. Moorthy

Status: open (until 19 Aug 2024)

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Srinivasan Prasanth, Narayana Sarma Anand, Kudilil Sunilkumar, Subin Jose, Kenath Arun, Sreedharan K. Satheesh, and Krishnaswamy K. Moorthy
Srinivasan Prasanth, Narayana Sarma Anand, Kudilil Sunilkumar, Subin Jose, Kenath Arun, Sreedharan K. Satheesh, and Krishnaswamy K. Moorthy

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Short summary
We study the impact of the 2019/2020 Australian bushfires on stratospheric chemistry and polar stratospheric cloud (PSC) dynamics. During Austral winter 2020, 82% of liquid nitric acid trihydrate (LNAT) PSC nucleated on bushfire aerosols, and 77% of ice PSC formed on these LNAT. This rapid conversion mechanism of LNAT to ice resulted in high anomalous ice PSC. This study sheds light on interactions between bushfire aerosols, and PSC microphysics which has significant global climate implications.