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Abstract The inorganic chlorine (Cly) and odd nitrogen (NOy) chemical families influence stratospheric O3. In January 2020 Australian wildfires injected record‐breaking amounts of smoke into the southern stratosphere. Within 1–2 months ground‐based and satellite observations showed Clyand NOywere repartitioned. By May, lower stratospheric HCl columns declined by ∼30% and ClONO2columns increased by 40%–50%. The Clyperturbations began and ended near the equinoxes, increased poleward, and peaked at the winter solstice. NO2decreased from February to April, consistent with sulfate aerosol reactions, but returned to typical values by June ‐ months before the Clyrecovery. Transport tracers show that dynamics not chemistry explains most of the observed O3decrease after April, with no significant transport earlier. Simulations assuming wildfire smoke behaves identically to sulfate aerosols couldn't reproduce observed Clychanges, suggesting they have different composition and chemistry. This undermines our ability to predict ozone in a changing climate.
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This content will become publicly available on September 28, 2025
Contrasting Chlorine Chemistry on Volcanic and Wildfire Aerosols in the Southern Mid‐Latitude Lower Stratosphere
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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- Award ID(s):
- 2316980
- PAR ID:
- 10582444
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 51
- Issue:
- 18
- ISSN:
- 0094-8276
- Subject(s) / Keyword(s):
- atmospheric chemistry volcano wildfire
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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