the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 03 May 2024
Characterization of AOD anomalies in September and October 2022 over Skukuza in South Africa
Abstract. This case study presents the evolution of aerosol optical properties during Intensive Observational Period (IOP) of the Biomass Burning Aerosol Campaign (BiBAC) in the Kruger National Park at Skukuza, between 18 and 23 September (Event 1) and 9 and 17 October (Event 2) 2022. The aerosol classification from sun-photometer data is consistent with the CALIOP, showing a predominance of biomass burning aerosols. The transport of CO and aerosols shows a southeastward transport over Southern Africa and toward the SWIO basin. The vertical distribution of aerosols spans vertically from the surface to 6 km (Event 1) and until 10 km (Event 2). The study discusses the synoptic conditions that have favored the significant perturbation of aerosol loading from September to October 2022. During Event 1, the "river of smoke" phenomenon was driven by surface ridge tongues with the westerly wave not being converted into a COL. During Event 2, a surface heat low, mid-tropospheric anti-cyclonic system, and warm air column resulted in stable conditions, which was also influenced by strong subsidence. The study investigates the long-range transport of biomass burning from South America to Southern Africa, with the plume exiting over southern Brazil, likely driven by the Southern American low-level jet (SALLJ), which is driven by climate forcings like El Niño–Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO). Further research addresses to the contribution of biomass burning plumes from Southern Africa and South America to those observed during both events and determines the atmospheric pattern.
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RC1: 'Comment on egusphere-2024-921', Anonymous Referee #1, 22 Jun 2024
This paper reports on smoke observations over southern Africa during September and October 2022 as part of the Biomass Burning Aerosol Campaign (BiBAC). The paper pulls together AERONET sun photometer data, CALIPSO/CALIOP lidar level 3 backscatter profiles, MODIS/IASI AOD and CO and CAMS aerosol analyses to describe a series of smoke events in and around Africa as well as a case of trans Atlantic transport from South America. After an overview of the intensive operations period each case is given a short observational summary meteorological analysis. I think overall it is publishable material and provides a needed overview of the meteorological conditions of BiBAC. This said, I am recommending major revisions largely on writing/communications issues.
Language is a little bit off throughout, which might be a language/translation issue. I think the paper needs a very solid edit to ensure clarity to the reader and use of proper meteorological diction. For example, in the abstract “anti-cyclonic system, and warm air column resulted in stable conditions, which was also influenced by strong subsidence.” The language is a bit odd, in that should the anticyclone have to be in an area of subsidence? Or was it an anticyclone that was imbedded in a larger region of subsidence or as part of a ridge? Also, perhaps it is cleaner to discuss “The study investigates the long-range transport of biomass burning from South America to Southern Africa, with the plume exiting over southern Brazil, likely driven by the Southern American low-level jet (SALLJ), which is driven by climate forcing like El Niño–Southern Oscillation (ENSO) and Madden-Julian Oscillation (MJO).” Is this part of the focus of the two events discussed earlier, separate? Further ENSO and the MJO are distinctly not climate phenomena, but rather seasonal and sub seasonal. These are just minor early examples, but throughout the read I was constantly trying to figure out what the authors are trying to convey. Another example, Introduction, line 55 “The vertical distribution of aerosols determines their radiative impact, as well as their atmospheric residence time, which will affect any aging processes and the resultant horizontal distribution following advection” One cannot really say generalities in such blanket statements, as depends on what radiative impact you are talking about, and the nature of the transport pattern. For shortwave fluxes, it makes almost no difference at all. If you talk about heating rates, then certainly. But also don’t intensive properties such as particle phase function and absorption coupled with concentration define the radiative effects? Other major issues include undefined acronyms and figure lettering that is to small to read. All of these issues get in the way of the reader extracting meaningful information. To be sure this is a useful effort, but please have another go and pay attention to proper technical term usage and I will be happy to give it another read.
Citation: https://doi.org/10.5194/egusphere-2024-921-RC1 -
AC1: 'Reply on RC1', Marion Ranaivombola, 03 Nov 2024
First of all, the authors acknowledge the referee 1 and the editor for the time spent to review this manuscript and also for their constructive comments. We regret for the language usage which has arisen the referee concern. The purpose of the present study is to highlight the transport modes which explain the transport of biomass burning plumes over the Southwest Indian Ocean (SWIO) basin during the BiBAC campaign. In order to clarify the objective of the paper, this latter was re-organized in the revised manuscript. In particular, Section 4 which treats on the synoptic and meteorological conditions driving the transport of the biomass burning plume during the BiBAC campaign was significantly re-organized in the revised manuscript. Indeed, this section was rewritten by corrected the inappropriate meteorological diction as suggested by the referee 1. In the revised manuscript, the AERONET data at level 2 was used in order to improve the significance of our results. To better characterize the synoptic conditions occurred during BiBAC, cloud cover products from CAMS reanalysis was added in the dataset used in this study. In order to emphasis on the synoptic conditions and not to extend the overall text length, we removed the paragraph mention about the aerosol size distribution evolution over Maputo. Thereby,the revised manuscript solely focused on meteorological and synoptic conditions driving the transport of biomass burning plume over SWIO basin. The motivations come from the fact that few studies treating on the transport of the biomass burning plume in the SWIO basin (Flamant et al., 2022; Swap et al., 2003; Schmid et al., 2003). These previous works pointed out a main transport mode over the SWIO basin which shaping like a river of smoke. In the present study, the structure of smoke river is also found but under different synoptic conditions than those reported by these previous works. We focused our effort to describe properly (with the appropriate language) these news synoptic conditions leading to river of smoke over the SWIO basin. These news synoptic conditions which occurred during the events detected during the BiBAC campaign are reported in the Figure 1 (This figure was included in the revised version, as Figure 13). In the previous works, the synoptic conditions responsible for the formation of the smoke river involved the propagation of a westerly wave and the development of a cut-off low (Swap et al., 2003; Stein et al., 2003; Flamant et al., 2022). However, we observed during the event 1 a river of smoke structure involved by westerly wave without a cut-off-low. The river of smoke developed in a synoptic context characterized by three successive cold fronts associated with saddle points during the event 2. Language usage has been appropriately corrected for the better readability of the article as suggested by the referee.
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AC1: 'Reply on RC1', Marion Ranaivombola, 03 Nov 2024
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CC1: 'Characterization of AOD anomalies in September and October 2022 over Skukuza in South Africa', Olakunle Ogunjobi, 26 Jun 2024
General Assessment: This manuscript presents an analysis of aerosol optical properties and transport during two events in September-October 2022 at Skukuza, South Africa, as part of the Biomass Burning Aerosols Campaign (BiBAC). While the study provides valuable data on aerosol characteristics during these events, there are several areas that require improvement to meet the standards of an EGU publication. The authors, however, need to improve their analysis, clarify their novel contributions, and improve the overall presentation of this paper. Reasons for this are as follows: Detailed Comments: Abstract (Lines 1-14): The abstract lacks quantitative results and clear statements of the study's novelty. Suggest revising to include key numerical findings and explicitly state how this work advances our understanding beyond previous studies. Introduction (Lines 15-88): The literature review is comprehensive, but the gap this study aims to fill is not clearly articulated. Suggest adding a paragraph (around line 85) that explicitly states the research questions and how they build on previous work. Line 70-72: The statement about few studies on the east coast needs supporting evidence. Consider citing specific gaps in the literature. Methodology (Lines 89-199): Lines 94-99: The description of the study site is good, but a map showing the regional context would be helpful. Lines 101-116: The use of Level 1.5 AERONET data instead of Level 2 needs more justification. What are the potential implications for the results? Lines 150-155: More details on the CAMS reanalysis product are needed, including its known biases or limitations in Southern Africa. Results and Discussion: Section 3 (Lines 200-250): The criteria for selecting the two events need more explanation. How do these events compare to typical conditions during the biomass burning season? Section 4 (Lines 251-355): The analysis of aerosol transport is informative, but could benefit from more quantitative assessment. Consider adding statistical measures of the spatial and temporal variability of AOD and CO. Section 5 (Lines 356-530): The discussion of synoptic conditions is detailed but could be more tightly linked to the aerosol observations. The comparison with previous "river of smoke" events (Lines 419-430) is interesting but needs more rigorous analysis. The discussion of intercontinental transport (Lines 460-499) is speculative and needs stronger evidence or should be significantly shortened. Figures and Tables: Figure 3: This figure is dense and hard to read. Consider splitting into two separate figures. Figure 4: The aerosol classification results are important but difficult to interpret. Consider using a different visualization method or adding a summary table. Figures 7 and 10: These synoptic maps are informative but could benefit from annotations highlighting key features discussed in the text. Scientific Approach: The multi-instrument approach is a strength, but the integration of different data sources could be improved. For example, a more quantitative comparison between AERONET, MODIS, and CALIOP data would strengthen the results. The analysis of vertical aerosol distribution (Lines 314-329) could be expanded, perhaps incorporating additional data sources or modeling approaches to better characterize the 3D structure of the aerosol plumes. Presentation and Language: The manuscript would benefit from careful editing for grammar and clarity. There are several instances of awkward phrasing or run-on sentences (e.g., Lines 380-385, 460-465). The conclusion section is missing. Add a concise conclusion that summarizes the key findings and their implications. Data Availability: A data availability statement is needed, detailing how readers can access the data used in this study. Compared to typical ACP papers I have seen in this line of research, this manuscript: - Provides a good multi-instrument dataset but falls short in the depth of analysis. - Lacks a clear articulation of its novel contribution to the field. - Needs improvement in the presentation of results, particularly in the figures. - Requires a more rigorous discussion that places the findings in the context of existing literature. For clarity, major revisions are needed to: - Clearly state the research questions and novelty of the work. - Improve the quantitative analysis of aerosol properties and transport. - Strengthen the discussion, particularly in relating the findings to previous studies and broader implications. - Enhance the quality of figures and tables. - Add a robust conclusion section. - Improve overall clarity and organization of the manuscript. In summary, while this study presents valuable observations, significant revisions are necessary to meet the publication standards of Atmospheric Chemistry and Physics.
Citation: https://doi.org/10.5194/egusphere-2024-921-CC1 - AC3: 'Reply on CC1', Marion Ranaivombola, 03 Nov 2024
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RC2: 'Comment on egusphere-2024-921', Anonymous Referee #2, 10 Sep 2024
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AC2: 'Reply on RC2', Marion Ranaivombola, 03 Nov 2024
First of all, the authors acknowledge the referee 2 and the editor for the time spent to review this manuscript and also for their constructive comments.
The purpose of the present study is to highlight the transport modes which explain the transport of biomass burning plumes over the Southwest Indian Ocean (SWIO) basin during the BiBAC campaign. In order to clarify the objective of the paper, this latter was re-organized in the revised manuscript. In particular, Section 4 which treats on the synoptic and meteorological conditions driving the transport of the biomass burning plume during the BiBAC campaign was significantly re-organized in the revised manuscript. In the revised manuscript, the AERONET data at level 2 was used in order to improve the significance of our results. To better characterize the synoptic conditions occurred during BiBAC, cloud cover products from CAMS reanalysis was added in the dataset used in this study. In order to emphasis on the synoptic conditions and not to extend the overall text length, we removed the paragraph treats on the size distribution evolution over Maputo. Therefore, we now solely focus on one scientific question in the revised manuscript : meterological and synoptic conditions driving the transport of biomass burning plume over SWIO basin. The motivations come from the fact that few studies treating on the transport of the biomass burning plume in the SWIO basin (Flamant et al., 2022 ; Swap et al., 2003 ; Schmid et al., 2003). These previous works pointed out a main transport mode over the SWIO basin which shaping like a river of smoke. In the present study, the structure of smoke river is also found but under different synoptic conditions than those reported by these previous works. We focused our effort to describe properly (with the appropriate language) these news synoptic conditions leading to river of smoke over the SWIO basin. In order to allow an easy read and understanding of these results, the quality of the English was checked in the revised manuscript (as suggested by the referee 2).
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AC2: 'Reply on RC2', Marion Ranaivombola, 03 Nov 2024
Video supplement
Aerosol Optical Depth at 550 from CAMS Reanalysis (September 18 to 23, 2022) Marion Ranaivombola https://doi.org/10.5446/67052
Aerosol Optical Depth at 550 from CAMS Reanalysis (October 9 to 17, 2022) Marion Ranaivombola https://doi.org/10.5446/67051
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