Investigating the Long-Range Transport of Aerosol Plumes Following the Amazon Fires (August 2019): A Multi-Instrumental Approach from Ground-Based and Satellite Observations

Round 1

Reviewer 1 Report

L67-79. Relevant references have to be included.

L102. "up to November"

L192 "cloud-free"

L203-204, omit "in the infrared, visible and UV bands, respectively"

L219 explain how much ppbv is the sensitivity +- values

L316 ground-based

L357 replace "They" by "These authors"

L391 replace "differences" by "significant variations on the recorded CO values"

L472 decide if you write "Event-1" or "event-1" through the manuscript

Comment: It would be fine if the authors could provide an estimation of the BB Radiative Forcing using atmospheric transmission models, to improve the current version of the manuscript.

Author Response

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Reviewer 2 Report

Specific comments

Lengthy abstract (please concise) and try to avoid discussing general well-known statements

Introduction

First two paragraphs can be deleted as they are general introduction about aerosols and its uncertainties. However, the information is not related to the present content of biomass burning. I appreciate the authors if they could begin the introduction from third paragraph

What do you mean by ‘arc of deforestation’

What does signifies the word ‘savannah-like’. Is it similar to the savannah climate or more or less the same. Justification required

The word ‘FLEXPART’ is described in the objectives as it appeared first time in the main text.

The motivation of study is not clear from the introduction or objectives and hence the authors are requested to work on the same for its inclusion in revised version of paper.

The authors have given more description about the satellite instruments in the data and methods section. Try to minimize the information to an possible extent as it is very general and well-known to the scientific community, retaining the website information from the data sets are procured.

The uncertainties associated in AERONET instruments are not described clearly. However, the use of level 1.5 in the present study violates the accuracy of data as the level 1.5 data is not quality assured (cloud-screened only). In what way, the authors have taken care to minimize the errors from using level 1.5 Aeronet data. Whether the authors have manually screened the data for quality check or any algorithm was developed for screening the data quality. Pls elaborate on the same

The authors have selected a month of observations for a particular year, August 2019. How the authors came to a conclusion for emission of BB smoke or fires from forest rather selecting the data period for different years during the same season. I recommend the authors to look in to the aspect rather than studying for a typical month of the year produces vogue results and is not clarified.

In figure 2, the authors have presented the number of fire pixels for the months in different years. How about the fire radiative power or intensity of fire. Hence it is mandatory to look in to the aspect of fire radiative power in the similar way as the authors have observed for different years of july and august months. The suggestion should be considered and analyse the information accordingly.

From figure 5, the daily value of AOD doesn’t exceed even 1.0. How can the authors arrive to the conclusion that is the dominance of BB smoke particles? Hence, recommending to present the Angstrom exponent values as well in association with the AOD which presents the particle-size.

The scale and corresponding labels are not clear in Figure 6a, 6c. please redraw the figures

It is not clear to the readers what are the inputs used by the authors in FLEXPART model for simulating air parcel pathways. Elaborate the same.

 

 

 

 

Author Response

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Reviewer 3 Report

This manuscript deals with the interesting topic, but the result does not support well the topic. The title includes the 'trans-Atlantic transport' but there is very small amount of this issue. Most of contents are just simple reading of AOD and CO data at given sites. Authors should focus on the characteristic of trans-Atlantic transport itself because the general pattern of trans-Atlantic transport is already well known. Also, the usage of satellite data is very limited to see the long-range transport, losing the merit of satellite data. Satellite can see the pattern over broad region. Why was this work limited to the usage of satellite data for targeted sites mostly? At least, this study need to add detail meteorology analyses related to the AOD and CO pattern from the satellite measurement.

- Grammer issue => Check the usage of 'the' for whole manuscript.
- Long abstract should be corrected (looks like the abstract)
- PM10, PM2.5 => number should be written in lower character
- L132: 3,9 => 3.9
- L137-138: => MODIS performs measurements at 36 different bands ...
- L260: fire activity => fire occurrence (MODIS provides several fire information: fire count, burned area, fire radiative power, and fire count indicates the 'frequency' of fire better than 'activity'. Fire activity is better described by the burned area or FRP. These values show a large different spatiotemporal pattern, so be careful for the discussion using only fire count information.
- L276-293 + figure 3: Trans-Atlantic transport is not clear compared to the dispersion of AOD and CO from the African region (related to the wildfire, too?). Obvious way to show the trans-Atlantic transport should be considered here for the revision. Figure 3 is not a good figure to illustrate the transport pattern. This is just 3-day mean AOD and 1-day CO pattern. In addition, this figure and discussion does not emphasize the meaning of this study, because CO and AOD is largely contributed from the Africa region. The role of CO and AOD from the Amazonian fire looks not significant. Why do we focus on Amazonian, instead of Africa? Authors should answer this question related to the motivation of this study.
- L316-342 + fig. 5: I do not think that this kind of analyses is necessary for the evaluation of trans-Atlantic transport. This is just comparison of AOD and CO between two sites in the same continent using different instruments (ground-based and satellite). In terms of the analysis of characteristics of trans-Atlantic transport, there is no meaningful message from this discussion.
- L343-368 + fig. 6: Lidar information is only available at Sao Paulo. How can we use this data for the analysis of trans-Atlantic transport?
- L394-399: I do not get it. More detail information should be required to support these statements. Fig. 3 is too general to illustrate clues of the detail discussion.
- L424-442: This is actually all statements, which are really related to the analysis of trans-Atlantic transport. This is not enough to derive the interesting feature of trans-Atlantic transport, which is already well-known. What is the fresh findings in this work? This is just a simple run of FLEXFART. Compared to previous works, what can we learn more about the properties of trans-Atlantic transport from this study?

Author Response

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Reviewer 4 Report

This research uses satellite data of fire products and AOD from MODIS and CO from METOP, supported by ground data and backward modelling, to track smoke plumes from Amazonian forest fires of 2019, across the Atlantic to southern Africa and the Indian Ocean. 

The results of the study do not match expectations however, as the gap in knowledge referred to in the Abstract and Introduction, is not supported ie. they claim in both Abstract and Introduction (45-46 and 75-77) that major sources of uncertainty lie in lack of knowledge of aerosol loading in source regions and estimations of radiative forcing and of aerosols. This leads us to expect these problems to be addressed in the paper, which they are not. Therefore the paper's objectives need to be better defined.

The evidence for smoke being transported to southern Africa (Lines 389-393) appears weak, based on the CO data alone. Authors already said in Introduction that S. Africa was a major source of BB aerosols in SH. Furthermore, Cape Town AERONET station was not working, and Reunion was not impacted by CO concentrations.  So how can you conclude that the increased CO was sourced in the Amazon? 

Specific comments

There appears to be some mismatch regarding the locations of fires described in the Introduction, Results, and Figure 3. Introduction states the 'Arc of Deforestation' to be eastern and southern edges of the Amazon (line 99). Yet Figure 3 in Results shows AOD only in western Amazon, not in east.

Similarly on Lines 302-303  Manicore is in western Amazon- this also contradicts line 99

In paragraph lines 108-117 discussing the Amazon region, you need a map showing where the Amazon is. However, Figure 1 is inadequate - a better map needed- where is 'the Amazon region'? What are the different shades of grey shaded areas
Why is the map cut off with no border at the top??
Brazil Bolivia and Peru mentioned in text should also be labelled on the map

Figure 3 also very messy -there is no legend for AOD maps, and dates on the top border of each map need to be standardised in terms of both format and font

Author Response

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Round 2

Reviewer 2 Report

The authors have considered all the suggestions and included the same in revised paper. The present revised paper is reached to the mark of journal and well qualified in its present form to consider for publication in remote sensing journal of MDPI. I appreciate the lead author and coauthors for coming out with original research contributed towards the transport of smoke. Hence, I strongly recommend the editor of journal and the journal team to publish the work in the current form. Congratulations to the authors and good effort.

Author Response

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Reviewer 3 Report

I do not think that the response is proper for suggested comments. Responses do not include the actual improvement but just the repetition of original analysis. I am sorry not to accept this level of response because the trans-Atlantic transport is well known issue, so more details are required for better understanding. Thus, I still think that authors should do more and detao; analyses to investigate the pattern of trans-Atlantic transport related to the Amazonian fire in 2019 if they would publish this manuscript in this journal. If authors would maintain the present form of this manuscript, submission to the lower-ranked journal is highly recommended.

Author Response

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Reviewer 4 Report

The authors have addressed three of my concerns. The maps are much improved, and the Objectives are better defined. Additional explanation about the FLEXPART model alays concerns about trans-Atlantic transport

However there remains some confusion about the location of the fires in the Amazon region, and although they have given some explanation in their reply, the text has not been modified. I acknowledge that this will not affect the main thrust of the paper, but the mis-match between text and figures needs to be addressed.

In their reply they state that

'Through the use of MODIS fire product, it can be observed that fires are widespread across theAmazon basin (see Fig. S1below). These observations are consistent with the fact that the bulk of the 2019 Amazonia fires waswithin the so-called “arc of deforestation” which traverses the southern and eastern edges of the Amazon basin'.

However, from the two figures supplied (Figure S1) it is clear that the '"bulk of the 2019 Amazonia fires" are in the southern and western Amazon, which corresponds with the AOD maps, and which show highest AOD in the west. 

Furthermore Figures 3g and h show plumes of AOD and CO crossing the Atlantic and emanating from the western Amazon, not eastern.

 

Grammar still has many problems

 

 

Author Response

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