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.

中文翻译：

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澳大利亚丛林大火排放导致极地平流层冰云增强


摘要。极端的丛林大火事件会排放温室气体和破坏碳汇，从而加剧气候变化，同时还会造成财产损失甚至死亡，造成经济损失。 2019/2020 年澳大利亚发生了一场这样的丛林大火，向平流层注入大量气溶胶和气体，消耗了臭氧层。虽然之前的研究重点关注臭氧消耗背后的驱动因素，但丛林大火对极地平流层云（PSC）的影响（臭氧消耗的一个重要因素）迄今为止尚未得到广泛研究。本研究重点关注丛林大火气溶胶对与 PSC 形成及其途径相关的动力学和平流层化学的影响。 Aura 微波临边探测器的分析显示，2020 年初，五氧化二氮水解作用增强，导致高纬度平流层下层硝酸 (HNO ₃ ) 显着增加。使用一种新方法从星载中检索 PSC 的形成途径通过激光雷达观测，我们发现增强的 HNO ₃ 在丛林大火气溶胶上凝结，形成 82% 的液体三水合硝酸 (LNAT)，并迅速转化为 77% 的冰，导致异常高面积覆盖冰 PSC。这突出了冰和 LNAT 的主要形成途径，可能有助于我们在气候模型中更好地模拟 PSC 形成和反硝化过程。由于对流层变暖预计将增加极端野火事件的发生频率，而平流层变冷预计将扩大 PSC 面积覆盖范围，因此这些发现将有助于更深入地了解极端野火事件对平流层化学和 PSC 动态的影响。