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Abstract Volcanic eruptions and wildfires can impact stratospheric chemistry. We apply tracer‐tracer correlations to satellite data from Atmospheric Chemistry Experiment—Fourier Transform Spectrometer and the Halogen Occultation Experiment at 68 hPa to consistently compare the chemical impact on HCl after multiple wildfires and volcanic eruptions of different magnitudes. The 2020 Australian New Year (ANY) fire displayed an order of magnitude less stratospheric aerosol extinction than the 1991 Pinatubo eruption, but showed similar large changes in mid‐latitude lower stratosphere HCl. While the mid‐latitude aerosol loadings from the 2015 Calbuco and 2022 Hunga volcanic eruptions were similar to the ANY fire, little impact on HCl occurred. The 2009 Australian Black Saturday fire and 2021 smoke remaining from 2020 yield small HCl changes, at the edge of the detection method. These observed contrasts across events highlight greater reactivity for smoke versus volcanic aerosols at warm temperatures.
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This content will become publicly available on September 16, 2025
Stratospheric Chlorine Processing After the Unprecedented Hunga Tonga Eruption
Abstract Following the Hunga Tonga–Hunga Ha'apai (HTHH) eruption in January 2022, significant reductions in stratospheric hydrochloric acid (HCl) were observed in the Southern Hemisphere mid‐latitudes during the latter half of 2022, suggesting potential chlorine activation. The objective of this study is to comprehensively understand the loss of HCl in the aftermath of HTHH. Satellite measurements and a global chemistry‐climate model are employed for the analysis. We find strong agreement of 2022 anomalies between the modeled and the measured data. The observed tracer‐tracer relations between nitrous oxide (N2O) and HCl indicate a significant role of chemical processing in the observed HCl reduction, especially during the austral winter of 2022. Further examining the roles of chlorine gas‐phase and heterogeneous chemistry, we find that heterogeneous chemistry emerges as the primary driver for the chemical loss of HCl, and the reaction between hypobromous acid (HOBr) and HCl on sulfate aerosols is the dominant loss process.
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- Award ID(s):
- 2316980
- PAR ID:
- 10582445
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Geophysical research letters
- Volume:
- 51
- Issue:
- 17
- ISSN:
- 1944-8007
- Subject(s) / Keyword(s):
- atmospheric chemistry volcano
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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