The manuscript reports the characterization of the stratospheric aerosols layer enhancements over Central Europe produced by explosive volcanic eruptions and severe smoke from big fires. To that end, lidar observations between 2017 and 2023 at Garmisch-Partenkirchen, one of the longest stratospheric aerosols lidar records is used.  It has been extensively used for research up to the present as the references show.   

The manuscript’s scientific significance and scientific quality are excellent. The presentation is also excellent.

The description of the main features of the lidar instrumentation evolution and the most relevant aspects of the retrieved signal processing are included appropriately. Also, the discussion in the Annex of the contributions to the aerosol backscatter uncertainties is very important. It addresses relevant scientific questions for ACP Journal, in particular the characterization of the vertical and temporal evolution of the stratospheric aerosol optical properties originated from severe smoke from big fires and explosive volcanic eruption.  All those facts warrantees the traceability of the results. The time frame are the last 6 years in which the frequency of those severe smoke from big fires has increased without a plausible explanation so far.

The scientific results and conclusions are presented in a clear, concise, and well structures way with an appropriate number of figures and tables.  It gives appropriate credit to similar research and clearly indicates its own contribution. The manuscript title is appropriated, reflecting its content. Similarly, the abstract provides a concise and complete summary.

The references area appropriated in quality and number as well as the supplementary material.

I have some comments and suggestions listed below.

Comments:

In the section “Spectacular pyro-cumulonimbus in British Columbia on 30 June 2021”, the Figure 8 shows the aerosol backscatter uncertainty profile allowing to appreciate its reasonable magnitude respect to the aerosol backscatter.  However, that is not possible for the two peaks going beyond the border of the figure.  I suggest the authors include a brief description of the relative magnitudes of the uncertainties at the peaks in comparison with the relative magnitudes of the uncertainties from the rest of the profile. 

Line 26: In the sentence: Ground-based lidar with its good vertical resolution became an important tool “almost” right from the beginning…. I suggest eliminating the word “almost” and add 2 more references:  Fiocco, G., and G. Grams, 1964 and Elterman et al., 1973.

The first series of stratospheric aerosol profiles from lidar (Fiocco, G., and G. Grams, 1964, https://doi.org/10.1175/1520-0469(1964)021<0323:OOTALA>2.0.CO;2 ) and from searchlight (Elterman, et al., 1964, https://doi.org/10.1175/1520-0469(1964)021<0457:AAOWSP>2.0.CO;2) were extensively used for research on stratospheric aerosol from the middle of the sixties (after the Mt Agung eruption) until around the end of the seventies. They contributed to characterize the volcanic stratospheric aerosols vertical profiles evolution and the further advance of the scientific knowledge in the sixties and early seventies of the XX century. That is evidenced by the multiple articles referencing those results, including the references to Fiocco and Elterman provided in the two papers already cited in that sentence: McCormick et al., 1978; Simonich and Clemesha, 1997. 

Elterman himself carried out research using Fiocco´s and his own datasets,                                            (ex. Elterman et al., 1973 https://doi.org/10.1364/AO.12.000330; Elterman,1976   https://opg.optica.org/ao/abstract.cfm?URI=ao-15-5-1113).

Line 342:  For clarity I suggest to change the sentence: ” The high lidar ratio suggested that observed at stratospheric aerosol at high latitudes were caused by import of fire smoke from Siberia.…”

By “The observed stratospheric aerosol high lidar ratio suggest its origin was the fire smoke from Siberia”

Line 487:  Is this sentence referring to figure 18.?  There is not an October 19 profile in the figure, unless the one from that month was labeled as October 10, before the date cited in the sentence. 

Line 1020:  The link http://www.trickl.de/Rayleigh.pdf does not work.

Figure 3:  4^th line in the caption.  The acronym “PSC” is not defined in the text, been used commonly for Polar Stratospheric Clouds.  The Quebec (1991) and Chilshom (2001) fires mentioned do not appear to be related to PSC events.  Please correct or clarify it.

Figures 7:  Add the wavelength the aerosol backscatter coefficient was measured.

Figure 12:  Briefly describe in the text the criteria to determine the upper and secondary boundaries of the top aerosol layer or provide a reference where it is described. Clarify the term main layer. Include in the caption the wavelength of the SCR. I suggest using the right axes scale for labeling the SCR magnitudes.

Review of Trickl et al., “Measurement report: Violent biomass burning and volcanic eruptions: a new period of elevated stratospheric aerosol over Central Europe (2017 to 2023) in a long series of observations”.

The manuscript by Dr. Thomas Trickl and coauthors presents the updated time series of stratospheric integrated backscatter from the 50-yr long lidar profiling record at Garmisch-Partenkirchen and focuses on the lidar observations of stratospheric aerosol layers produced by intense wildfires and volcanic eruptions since 2017.

The authors should be congratulated for an impressive effort to produce such a long-term and high-quality observation record of stratospheric aerosol loading as well as for their rigorous approach to data quality and error budget assessement.  

The manuscript is well structured, the experimental setup and the quality aspects are described in a comprehensive way, whereas an appropriate credit is given to the related literature. Overall, the study represents a valuable contribution to the stratospheric aerosol problematics from the observational perspective.

 In my opinion, the study could potentially be a good match for the “Research article” category had it included a more profound analysis of the locally observed features (beyond attribution to a specific event using simple trajectory modeling), or had it provided new information on the aerosol optical properties from various sources or otherwise re-evaluated different transport pathways and their timescales. While there are several novel aspects invoked (e.g. BDC-driven transport of aerosols, prolonged stratospheric aerosol decay etc.), the related interpretation largely rests upon general considerations without appropriate support from other data sources, in particular the global observations.

The high-quality local observations presented in the paper will surely motivate further research on the topic using global observations and modeling experiments. Therefore, in no way the “Measurement report” category could reduce the scientific impact of this paper. I recommend it for publication in ACP after a few minor revisions as suggested below.

Specific remarks

l.336-337. It is indeed very interesting (and also puzzling) why the backscatter enhancements are restricted to the lower part of the ozone enhancements. Could it be linked to aerosol sedimentation within the intruded airmass? I would be extremely curious to see the time curtains of backscatter (or just the range corrected signal) together with ozone curtain if this is not too much work.

l.379. Is the upper boundary of enhanced aerosol layer at 19.5 km attributed to wildfire smoke? To my knowledge, neither OMPS-LP nor CALIOP have reported aerosol layers this high during that time. If it were a smoke layer at this altitude, one should expect a significant self-lofting of highly-concentrated plumes prior to this lidar measurement, which would be readily detected by satellite sensors.

l.435-440. While the wildfire smoke could, to some extent, contribute to the SA load perturbation after Summer 2019, I believe that the prolonged decay is largely due to the self-lofting of Raikoke sulfur-coated ashes as argued upon in this study https://www.nature.com/articles/s41598-022-27021-0 The self-lofting of aerosols is expected to prolong the aerosol removal from the stratosphere through gravitational settling.

l.439-440. I am unconvinced that the layers above 30 km could be attributed to Ulawun sulfates, please see my further remark on that matter.

l.498-509. The detection of hydrated layers from Hunga using RS and lidar in the northern midlatitudes is certainly an important result, however this should be supported by the respective graphical material.

l.548-552. In terms of the amount of injected material and injection altitude, the Ulawun eruption is nowhere near that of the 1991 Pinatubo eruption. Thus, appealing to modeling results by Stenchikov et al. for a major eruption appears to me unjustified.

l.557-558. Indeed, the absence of aerosols beyond 32 km after Pinatubo puts in doubt the attribution of layers above 30 km to the eruption of Ulawun. During the BDC-driven transport to midlatitude, the Ulawun sulfates would be exposed to warm temperatures and evaporate. This explains the absence of volcanic aerosols transported from the tropics at such altitudes. A much more plausible source of the high-altitude aerosols observed by the GP lidar, in my opinion, is the Australian ‘’Black Summer” PyroCb outbreak that generated a smoke-charged vortex rising up to 35 km whilst travelling towards the tropics. The fine smoke particles sediment slower than sulfuric acid droplets, which further corroborates this hypothesis. Another potential source could be the meteoritic dust. While an accurate attribution of the observed feature would require a careful analysis of various satellite data and transport modeling, I suggest elaborating this discussion a bit to consider various potential sources.

l.582. One should also mention particle sedimentation (e.g. Kremser et al., 2016), which does not fall under strat-trop transport category.

l.583. As far as the dilution and advection of clean air masses are concerned, it might be worth referring here to Vernier et al., ACP, 2011 and Khaykin et al., ACP, 2017 pointing out the poleward transport of convectively-cleansed air from the tropical tropopause region.

General comments:

This paper documents one of the longest lidar records of stratospheric aerosols in existence.  Changes in the instrumentation and analysis are followed through the record, and their implications for the data  are assessed.  Numerous volcanic eruptions and wild fires impacting this mid-latitude site in Germany are identified from sources in both the Northern and Southern hemispheres.  This is a useful compilation for those wondering if a specific event impacted this region of the earth at a certain time.  The absolute differences between events can also be reliably compared.

The paper is well written and only minor changes are suggested.

Specific comments:

Abstract: no comments

Line 45: Do you mean lifetime or 1/e folding time?  I usually see about 1 year for these?

Line 129: “expensive additional laser photons”,  do you mean you can use a smaller laser?

Line 153:  The field campaign didn’t involve lidar right? It isn’t portable, but was controlled from the United States?

Line 165: “Afterwards, an extended-Klett (Klett, 1985) program, originally developed and very successfully quality assured for aerosol retrievals within EARLINET, is used”

Line 193: “The counting noise level in the raw data descends with altitude” Do you mean decreases with altitude?

Line 283:  “(2018 “ missing “)”

Line 330:  “…Northern Canada tree…”?

Line 430:  “The temporary minimum of the integrated backscatter coefficient in September, 2019 is caused …”?

Line 494:  “Not always stars exist …”?

Line 505:  What do you mean by depolarized particles?

Figure 4:   caption, “…Munich tropopause altitudes from the Munich radiosonde …”

Figures 16, 18, 19:   Can you show the color scale?  If all three figures use the same scale you could show the scale for just figure 16 and refer to that in 18 and 19.