Review for Antuña-Marrero: "Extending the late 1963 to 1964 Mt Agung rescued searchlight aerosol profiles dataset at 32N, from early 1963 to 1976."

The 1963 Mt. Agung eruption was one of the most significant volcanic events of the 20th century, yet its long-term climate impact remains poorly understood because very little is known about the transport and vertical distribution of its stratospheric aerosols. Before the satellite era, most publications relied heavily on indirect measurements such as ice core data and astronomical observations of starlight attenuation. This lack of high-resolution vertical profiles means current climate models often rely on poorly constructed datasets for evaluation; hence, there is a limited understanding of how these aerosols evolved over time. The rescued searchlight data presented in this manuscript addresses this critical gap for both the 1963 Agung and 1974 Fuego eruptions.

The manuscript identifies two critical features in the rescued dataset. First, observations from March and April 1963 reveal an early arrival of stratospheric aerosols at 32N, directly contradicting the accepted view that these aerosols only reached northern midlatitudes in the second half of 1963. Second, the joint series shows anomalous increases in stratospheric aerosol optical depth during late 1964, a period previously thought to be characterised by a simple decay phase. The authors also estimate the optical depth values at 0.019 and 0.040 before and after the arrival of the aerosol cloud, respectively. These findings demonstrate that the post-Agung stratosphere was significantly more complex than existing understanding suggests. Consequently, this research is an important component of the SSiRC Data Rescue Activity. Integrating these rescued searchlight profiles with lidar records provides the necessary synergy for a robust foundation for quantifying volcanic forcing. Most of the modelling studies (e.g. Dhomse et al. (2020)), highlighted difficulties in identifying consistent aerosol optical depth datasets across multiple instruments. Overall, it is a well-written manuscript describing an important dataset, and I recommend it for publication.

Minor Comments:

1. Title: Figure 3 and other tables clearly indicate that May 1975 is the end date, so the title should not state 1976.
2. Figure Quality: The quality of the figures should be improved for the final version of the manuscript.
3. Altitude Range: There is a discrepancy in the defined altitude range for the sAOD calculation; for example, the abstract and section 2.2 mention the 12 to 25 km layer, but other places, such as table 3 and section 3.2, state it is 15 to 25 km.
4. Citation Error: At line 153, the text states that ATP were reported both in Elterman et al. (1973) and Elterman et al. (1973), which is a redundant citation that should be corrected.

General comments:

This paper describes rescued and digitized data sets of stratospheric aerosol extinction (and turbidity) based on searchlight measurements carried out in the U.S. in the 1960s and 1970s. The data sets are important for the atmospheric science community and I think the paper should eventually be published. I ask the authors to consider the comments below.

I have two general comments:

1. Although the complexity of the study is not very high, the description of the different profiles is not easy to follow and I suggest restructuring the introduction of the different profile types (introduce AEP_c and AEP_d in two subsequent sentences). At some point AEP_s appears and it is unclear to me, whether this is a typo; I assume that.
2. Is it possible to provide an error estimate for the extinction coefficients and the sAODs? The background values (before the arrival of the volcanic plume in spring 1963) are already quite high, both for the extinction coefficient and sAOD. This data set is of course only useful for climate modelling, if it is accurate and/or an error estimate exists.

Specific comments:

Line 15: “digitization’s errors” -> “digitization errors”

Line 20: “This fact”

In the previous sentence you wite "what could be", now it is suddenly a fact?

Same line: “the arrival .. arrived”

Please adjust/correct.

Line 28: space missing in Fontijn reference.

Line 29: Delete “the” in “Before the 1979”

Line 40: “the datasets have not been available at any data repository/archive for more than half a century.”

The data set probably has never been available, right? The sentence allows the possibility that they were available at the beginning and then not any more.

Line 52: “consists on” -> “consists of”

Line 55: “has been” -> “have been”? I think the sentence is incomplete or misleading. Please check, whether intended meaning and actual meaning match.

Line 70: “at the same night” -> “in the same night”

Line 82 and lines 90, 125: “on Table” -> “in Table”

Same line: “the others” -> “the other”

Same sentence: “have been digitized”

By whom? Probably by you as part of the current study. From the way this is expressed it is not clear, whether this was done in past study or within the current study. Please state it explicitly.

Line 84: “The plots digitization” -> “The plot’s digitization” or probably better “The plot digitization”

Line 86: “The 11 ATPs and 2 AEPs plots” -> “The 11 ATP and 2 AEP plots”

Line 91: “The second column reportS”

Equation (2): I wonder, why the digitization is necessary, if the values are published in papers? Perhaps values are only published for a subset of the profiles (I'm getting confused with all the different profile abbreviations). If yes, I suggest stating this here explicitly. Thanks.

Lines 128 and 129: “RME”

Above you define “MRE”, not “RME”

Line 146: “respect to” -> “with respect to”?

Paragraph starting line 147 and also definition of the different profiles above: I read the corresponding section several times and I think the overall description of the different profiles and the difference between AEP_c and AEP_d can be and should be improved. "AEP_d" appears first in line 114. I suggest explaining in subsequent sentences, what "AEP_c" and "AEP_d" mean. Currently, the text is not really easy to follow.

Line 152: “currently missed”

I don’t really understand what this refers to? Please explain in text.

Lines 164, 171: “on figure/s” -> “in figure/s”

Line 165: 3 occurrences of “AEP_s” (with subscript “s”): What are these profiles now? Something new? Or a typo and it should be “AEPs”?

Line 173: the sAOD before the arrival of 0.019 is already quite high and significantly higher than typical background sAODs, right? It would be good to discuss that and also, how reliable these sAOD values are in general.

Line 177: 2 occurrences of “AEPc” -> “AEP_c”

Line 188: “which length” -> “whose length”

Line 190: “that the last sAOD value”

Meaning unclear, the last sAOD value shown in the Figure is in 74/75, but you mean daily values in 1964 here, right? Please correct.

This paper covers the extension of the recovery of data during the pre-satellite period of stratospheric aerosol observations particularly in the time frame of the 1963 Agung eruptions. These data sets are extremely valuable and the dedication of the authors to this mostly thankless task is a true service to the community.  The paper describes the process of data recovery well and I support publication of this paper with some minor revisions enumerated below.

The primary concern I have is that, since I am not terribly familiar with search light measurements, I don’t appreciate the measurement process or the uncertainties associated with these measurements.  A brief discussion of how the measurements are made (a paragraph) would be helpful. Also, the paper describes digitization differences between the historical tabulated data and the digitized data record produced in this paper but does nothing to provide the reader with any idea how this data could be used in practice. For instance, I find the profiles in Figure 1 look unrealistic at higher altitudes and wonder how good the profiles are at those altitudes and by extension throughout. In addition, the scatter shown in Figure 3 is so large after the eruption of Agung that I wonder about how robust the original measurements are. How much of the scatter is related to the difficulty of making the measurements and how much represents real geophysical variability?  I recognize that the authors do not have access to the raw data but, at this point in time, they may have more insight into the difficulties of making these measurements than anyone else and it would be extremely helpful to elucidate these issues to their potential users.

I worry a bit about using a fixed 12 km tropopause altitude in the sAOD calculations since that altitude can be quite variable and, particularly in the Summer, it can be quite a bit higher than 12 km so some tropospheric aerosol would be included in a stratospheric value. I recognize that part of those calculations is meant to produce comparable values to those reported but some clarity on that would be welcome.

In general, the extinction referred to in the manuscript would be more correctly referred to as extinction coefficient.

The grammar is stilted at times throughout the paper.

Line 42  I think SSiRC has been renamed recently though it is well known by the former name.

Line 55 It might be worthwhile to mention the recovery of the post El Chichon NASA aircraft lidar data as a part of GloSSAC and available at the NASA Atmospheric Sciences Data Center.

Line 75 You could probably eliminate equation 1 and just refer to

ATP(z) at 0.55 microns is determined as the ratio of the original published extinction coefficient profiles and the Rayleigh (molecular) extinction profiles found in Elterman (1964).

Line 118-123  I don’t understand the discussion of estimated errors.  Is this just the difference between tabulated errors versus the digitized values?  If so, the discussion should be clearly referred to as digitization uncertainty.  (later on this becomes clearer)

Line 159 Focused with one s is much more usual.