Preprints
https://doi.org/10.5194/egusphere-2023-995
https://doi.org/10.5194/egusphere-2023-995
16 May 2023
 | 16 May 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2021) observations of smoke in the stratosphere

Larry W. Thomason and Travis N. Knepp

Abstract. Using a common analysis approach for data sets produced by the Stratospheric Aerosol and Gas Experiment instruments SAGE II and SAGE III/ISS, we identify 13 likely smoke events based on enhancements in aerosol extinction coefficient. Nine of these are sufficiently large compared to ambient aerosol levels to compute mean mid-latitude 1020-nm optical depth enhancements that range from 0.0005 to 0.011. We also note that, for large events, the 525 to 1020 nm aerosol extinction coefficient ratio asymptotes at high extinction coefficient to values between 2 and 3 suggesting that the aerosol is relatively small (<0.3 μm) and relatively consistent from event to event. Most of these events are primarily confined to the lower stratosphere and rarely can be observed above 20 km. We also infer an increase in the frequency of smoke events between the SAGE II (1984–1991, 1996–2005) and SAGE III/ISS (2017–present) periods by almost a factor of two and also note that the two largest events occur in the latter data set. However, given the low frequencies overall, we are not confident that the differences can be attributed to changes between the two periods. We also attempt to disentangle the mixing of aerosol in the northern hemisphere summer of 1991 from a pyrocumulus event (Baie-Comeau, Quebec) and Mt. Pinatubo and conclude that, while there is evidence for smoke in the lower stratosphere, virtually all of the enhanced aerosol observations in the northern mid-latitudes in the summer of 1991 are associated with the Mt. Pinatubo eruption.

Larry W. Thomason and Travis N. Knepp

Status: open (until 27 Jun 2023)

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  • RC1: 'Comment on egusphere-2023-995', Anonymous Referee #1, 30 May 2023 reply

Larry W. Thomason and Travis N. Knepp

Larry W. Thomason and Travis N. Knepp

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Short summary
We examine space-based observations of stratospheric aerosol to infer the presence of episodic smoke perturbations. We find that smoke's optical properties often shows a consistent behavior though vary somewhat from event to event. We also find that the rate of smoke events observed in the 194–2005 period is about half the rate of similar observations in the period from 2017 to the present though with such low over all rates inferring change between the periods is difficult.