the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Quantifying SAGE II (1984–2005) and SAGE III/ISS (2017–2021) observations of smoke in the stratosphere
Larry W. Thomason
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
For technical reasons the paper cannot be accepted in its present form.
The figures must be improved.
We teach our students to prepare proper figures and to consider all basic rules when designing figures and plots! Therefore I cannot accept figures in which so many standard requirements are ignored and violated.
Before I come to the figures, one question: What do you mean when you state: the aerosol is relatively small (<3µm). You mean the radius (?) of the aerosol particles or do you mean the diameter (?) of the aerosol particles? The aerosol consists of molecules and particles and cannot be small.
Figure 1: There is no x-axis text (Extinction coefficient (1/km)) and no y-axis text (Year)! This is unacceptable! The unit of the extinction coefficient (km-1) is not mentioned! Must be improved! Instead of 30-60N, please write: 30°-60°N, everywhere in the text.
Figure 2: x-axis: please add unit of the Extinction Coefficient …. (1/km). Three times!
Figure 3: The numbers of isolines in the color plots are not readable. To my opinion, the color bars are not acceptable. Too complicated. I would prefer two color scales, one for the extinction coefficient and one for the ratio.…..But this is just a suggestion!
y-axis: Latitude ….. better: Latitude (°N). Please improve this in Figs. 4, 5, 6, 9,1 0, 11, 12, 13, 14,16.
Figure 4: x-axis: ‘1020-nm Aerosol’ should be changed to ‘1020 nm Extinction Coefficient (1/km)’
Figure 5: Days: 121 – 150 is wrong, you state in the caption: 151 – 180.
x-axis: ‘1020-nm Aerosol’ should be changed to ‘1020 nm Extinction Coefficient (1/km)’
Figure 6: x-axis: ‘1020-nm Aerosol’ should be changed to ‘1020 nm Extinction Coefficient (1/km)’
Figure 7: x-axis ‘1020 nm Extinction Coefficient (1/km)’ … unit is missing!
The horizontal line is sometimes at 3, sometimes at 4! Is there a reason for this?
There is room in all the plots to include the location (which is given in the caption).
I have the feeling the data in (i), 2020: 181-210, and in (j) are the same (2021: 181-210)
Figure 9: Almost ‘perfect’ x-axis and y-axis text! Only Latitude… could be improved to …. Latitude (°N).
Similar comment (as for Fig.9) regarding the rest of the figures.
Citation: https://doi.org/10.5194/egusphere-2023-995-RC1
Larry W. Thomason and Travis N. Knepp
Larry W. Thomason and Travis N. Knepp
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