General comments:

This paper aims to provide an overview of the aerosol optical and microphysical properties during SLOPE I and II field campaigns in Granada using the GRASP remote sensing retrieval algorithm. GRASP retrievals were validated with in-situ measurements (with nephelometer, aethalometer, SMPS, CPC, and APS) performed at the Sierra Nevada Station and airborne flights (nephelometer, aethalometer). This study shows that GRASP retrieval algorithm can provide a valuable addition to the in-situ measurements and climate models

Abstract:

Line 20-22: Sentence needs rewording

Line 35: “study the aerosol properties profiles” ? – This sentence needs rewording.

Line 38: “simultaneous in situ measurements”. Please introduce the instruments here.

Specific comments:

“In situ” or “in-situ”, please be consistent

Line 61: “while they have”

Line 65: “provide information”, instead of “have information”

Line 114: “very variable” – without the world “very”

Line 149: “that operates”

Lines 160-161: “that performs…atmosphere” – needs rewording

Line 191: How about at 20 μm diameter?

Line 193: For consistency purposes, can you stick on just radius or diameter?

Line 194: It would be nice to provide a brief explanation what Q value is

Line 208: “divide the sampled air” instead of “de”

Line 225: From lidar? It would be nice to mention the instrument here

Line 227: Is this a necessary condition to run GARRLiC?

Line 240: “between minimum”, without “a”

Line 246: What does relative residual mean? What was its magnitude at the current case?

Line 255: “pressurized”

Line 258: What is the uncertainty on the measurements from using temperature obtained from MWR, instead of having a temperature sensor outside the aircraft?

Line 295: Have you tried to run GRASP in 1-mode? A related paper to cite here is Kezoudi et al, 2020, where the authors used 1-mode size distribution ("We constrain the investigation in this study to one dust mode because the UCASS observations at Cyprus show a dominance of coarse-mode dust particles throughout the atmospheric column...")

Kezoudi, M., Tesche, M., Smith, H., Tsekeri, A., Baars, H., Dollner, M., Estellés, V., Weinzierl, B., Ulanowski, Z., Müller, D., and Amiridis, V.: Measurement report: Balloon-borne in-situ profiling of Saharan dust over Cyprus with the UCASS optical particle counter, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2020-977, in review, 2020.

Line 323: Can you please elaborate on the purpose of the differences?

Line 369: You probably mean “Box-Whisker”?

Line 375: “of non-absorbing particles”… e.g. dust

Line 380-382: Any reference for this?

Line 389: that come from the Atlantic brings...

Line 416: *patterns (plural)

Line 420: How about the altitudes, any references?

Line 425: *reveals

Line 426: Does this stand for all the aerosol types?

Line 429: Please elaborate on that, give some threshold values for both

Line 430: What do you mean with "intensive" properties?

Line 435: obtained from where? Here? In Muller et al?

Line 436: … to the ones observed…

Line 440: at these levels which are dominated…

Line 439-442: Reword this sentence please, it is too big

Line 446: *pollutants

Line 448: were occurred/observed, instead of “registered”

Line 457: *in the morning

Line 459: “in our region”? Do you mean in Europe? Spain? Granada?

Line 460: affect both the intensive…

Line 464: *in the aerosol layer

Line 469: *as shown in Bevanent

Line 474: “very similar”, please provide some numbers

Line 477: “as expected for mineral dust particles”, any potential reason for that?

Line 478: *are supported

Line 501: “due to the few cases”, is this the reason? If there were more cases, then would the agreement be better?

Line 506: *for both scattering

Line 521: *of these events

Figures:

Figure 1: It would be nice to show information about the altitude

Figure 10b: The scale in x axis should be adjusted to the corresponding magnitude. This is too large and lines cannot be seen clearly.

General comments

The paper offers an overwiev of the remote sensing, in situ and aircraft measurements done in SLOPE campaings at Granada. In addition, it is aimed at testing GRASP performance, using the configuration combining photometer and lidar, in determining microphisical and optical aerosol properties. These retrievals have been validated against in situ and aircraft measurements. The validation results confirm the feasibility of GRASP to characterize the aerosol properties in different aerosol conditions and show its potential to analysze high-load aerosol events (dust and biomass burning).

These results provide significant information for the operative use of GRASP retrievals in climate studies.

The paper is well written and structured. It is well written and structured and fits perfectly with the aims and scope of the ACP journal and the research interests of its readers. 

Specific comments

Instrumentation

At the begining of the site and measurements section  (Sect. 2) the authors assert that airplane measurements on board of Partenavia P68 airplane were done (L132). However the instrumentation described in sect. 2.3 is referred to flights carried on by a Piper PA 34 Seneca airplane. As far as I know they are two different types of airplane. Can you explain this or correct it, if needed?

Results

L372. There are different papers in the literature that revealed larger absortion in the UV for mineral dust in the Mediterranean region, that is not observed in this work. Do you have any explanation about it?

L382. Apparently there is contradictory information in this paragraph. First, in L174 the authors assert: ...relative large values of SSA for all wavelengths indicate important fraction of non-absorbing aerosol particles. And then in L382. "GRASP has

revealed the large contribution of aerosol absorption in total aerosol optical depth during SLOPE I and II field campaigns even for cases with relatively low AODs"

Please, explain it better.

L426. The sentence: " ..GRASP retrieval...." should be rewritten for a better understanding. 

L93. Please change "allow" by "allows"

L132. Please change "allow" by "allowed"

Figures

Fig. 6. Since the figure represents a time serie, please add stright lines joining the markers to an easier view of the evolution.

This paper addresses an evaluation of the aerosol property profiles retrieved from GRASP algorithm and which uses as inputs lidar and sun-photometer (SPM) measurements versus in-situ measurements. The in-situ measurements were carried out at Sierra Nevada Station (SNS) and on board of an aircraft.  The work presents different relevant aspects that show its importance and novelty. This is the first time that GRASP algorithm using as inputs lidar and SPM measurements (GRASP) has been evaluated for absorption coefficient in a long-term comparison. In addition the work have dealt with the complexity of comparing different techniques (remote and in-situ) which also cover different ranges in the Earth-atmosphere system (surface and almost full troposphere). The results presented here show a good agreement between the optical properties from techniques and larger discrepancies in the volume size distribution when fine particles are dominant.

So after these comments I conclude that the paper is very interesting, well written and show the capability of GRASP approach to retrieve vertical information of aerosol properties based on this long-term study. I consider that this work is appropriated for Atmospheric Chemistry and Physics and it should be published after some minor corrections:

Specific comments:

Line 23 -26: Sentence needs rewording

Lines 65 - 69: If you have elastic and inelastic signals you can also calculate the backscatter coefficient using the Raman techniques, which present the advantage that you don’t need any assumption of LR. So please be more precise in this sentence, it sounds that you only can calculate the backscatter coef. using klett method.

Line 75: replace “retrievals”  by “retrieval”.

Lines: 100 – 104: Confusing sentence: I imagine that you mean that the combination of SPM and ceilometer allows obtaining less optical properties than using multi-wavelength lidars, but the sentence should be more explicit. The authors refer “long-term vertical profiles” from the combination of SPM and ceilomter, it is difficult to know what you mean.

Line 207: d.o.o. : Can you say what it means for the first time that is cited in the manuscript?

Line 8: Please, replace “de” by “the”.

Methodology. General comments: I recommend to put the description of GRASP in a subsection, for example 3.1, in order to put it at the same level than aircraft data section. In addition, I suggest including in this section a paragraph talking about the lidar inversions. I guess that you are using the Klett algorithm to obtain the backscatter profiles, but it should be indicated. If this is the case, the assumed lidar ratio and the criteria for choosing those values should be discussed.

Lines 235-236: This sentence should be clarified. The sentence mixes GRASP and LIRIC algorithms, with an inversion method (for lidar measurements, which is not indicated) with a measurement technique (in-situ). It should be more elaborated to make it more understandable.

Results. General comments: The statistical analysis should be better described. The number of the cases (profiles) used for the different analyses is not mentioned at any time.

Lines 276 – 277: Please rephrase the sentence. You could write something like: “The aerosol volume concentration at SNS were calculated for the 0.05 – 0.5 and 0.5 – 10 μm radius size ranges for the fine and coarse modes, respectively.

Lines 317 – 318: It should be mentioned that is at 532 nm. Why is it not calculated for other wavelengths? How is it calculated the extinction from in-situ? Did you use the sum of the scattering and absorption from different in-situ instrument? This should be indicated in the manuscript, perhaps in the methodology section.

Figure 6: For clarity, it should be helpful to indicate the year for each plot of the figure.

Lines 408 – 409: “The decays do not reveal any decoupled layer with altitude”: This statement is difficult to corroborate when all the profiles are plotted. I guess that for some individual profiles decoupled layers of the Planetary Boundary Layer could be present.

Lines 420: Comment: The shape of the profiles does not look like exponential.

Line 471: “For intensive optical properties, …”. Do you mean “extensive” ?