Stratospheric ozone depletion inside the volcanic plume shortly after the 2022 Hunga Tonga eruption
<p>Near-term in-plume ozone depletion was observed for about 10 d by the Aura Microwave Limb Sounder (MLS) right after the January 2022 Hunga Tonga–Hunga Ha'apai (HTHH) eruption. This work analyzes the dynamic and chemical causes of this ozone depletion. The results show that the large wa...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/13355/2023/acp-23-13355-2023.pdf |
| Summary: | <p>Near-term in-plume ozone depletion was observed for about 10 d by the Aura Microwave Limb Sounder (MLS) right after the January 2022 Hunga Tonga–Hunga Ha'apai (HTHH) eruption. This work analyzes the dynamic and chemical causes of this ozone depletion. The results show that the large water injection (<span class="inline-formula">∼</span> 150 Tg) from the HTHH eruption, with <span class="inline-formula">∼</span> 0.0013 Tg injection of ClO (or <span class="inline-formula">∼</span> 0.0009 Tg of HCl), causes ozone loss due to strongly enhanced HO<span class="inline-formula"><sub><i>x</i></sub></span> and ClO<span class="inline-formula"><sub><i>x</i></sub></span> cycles and their interactions. Aside from the gas-phase chemistry, the heterogeneous reaction rate for HOCl <span class="inline-formula">+</span> HCl <span class="inline-formula">→</span> Cl<span class="inline-formula"><sub>2</sub></span> <span class="inline-formula">+</span> H<span class="inline-formula"><sub>2</sub></span>O increases to 10<span class="inline-formula"><sup>4</sup></span> cm<span class="inline-formula"><sup>−3</sup></span> s<span class="inline-formula"><sup>−1</sup></span> and is a major cause of chlorine activation, making this event unique compared with the springtime polar ozone depletion where HCl <span class="inline-formula">+</span> ClONO<span class="inline-formula"><sub>2</sub></span> is more important. The large water injection causes relative humidity over ice to increase to 70 %–100 %, decreases the H<span class="inline-formula"><sub>2</sub></span>SO<span class="inline-formula"><sub>4</sub></span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="62d2c8208bbdf49afb8db19c9f7b6b50"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-13355-2023-ie00001.svg" width="8pt" height="14pt" src="acp-23-13355-2023-ie00001.png"/></svg:svg></span></span> H<span class="inline-formula"><sub>2</sub></span>O binary solution weight percent to 35 % compared with the 70 % ambient value, and decreases the plume temperature by 2–6 K. These changes lead to high heterogeneous reaction rates. Plume lofting of ozone-poor air is evident during the first 2 d after the eruption, but ozone concentrations quickly recover because its chemical lifetime is short at 20 hPa. With such a large seawater injection, we expect that <span class="inline-formula">∼</span> 5 Tg Cl was lifted into the stratosphere by the HTHH eruption in the form of NaCl, but only <span class="inline-formula">∼</span> 0.02 % of that remained as active chlorine in the stratosphere. Lightning NO<span class="inline-formula"><sub><i>x</i></sub></span> changes are probably not the reason for the HTHH initial in-plume O<span class="inline-formula"><sub>3</sub></span> loss.</p> |
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| ISSN: | 1680-7316 1680-7324 |