the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 Apr 2025
A Novel Framework for Assessing Regional Wildfires Contributions to Biomass Burning Aerosol Optical Depth
Abstract. Biomass burning (BB) aerosol significantly affects climate by altering the radiation budget and atmospheric chemistry. Accurate source estimation is vital for climate modeling, yet global observations remain scarce. This study introduces a novel framework for assessing the contribution of transported BB aerosol to smoke-associated aerosol optical depth (BB AOD) at selected locations. The approach integrates satellite fire data (MODIS Active Fire Product) with air parcel trajectory models (HYSPLIT), aerosol transport models (NAAPS), BB emissions (FLAMBE), and plume rise (CAMS GFAS).
Tested in Warsaw (Poland, Central Europe) over 2006–2022, the methodology reveals a prominent influence of long- range BB aerosol transport from North America. Analysis indicates that Canada (33.2 % ± 2.4 %) and the USA (32.8 % ± 7.6 %) together contribute approximately 66 % of BB AOD during the BB season in the Northern Hemisphere, surpassing nearer European sources. Among European regions, Eastern Europe accounts for 16.5 % ± 3.2 % of BB AOD, followed by the Iberian Peninsula (11.4 % ± 2.8 %) and Southern Europe (6.1 % ± 1.0 %). Incorporating vertical plume dynamics is crucial: a fixed plume-top threshold of 2250 m underestimates elevated Canadian plumes while overestimating lower European sources, whereas removing altitude constraints overestimates Canadian influence. These findings underscore the importance of transatlantic transport, plume-rise processes, and vertical aerosol distribution in regional climatology.
The presented framework for assessing BB AOD contributions is universal and can be applied at any location. Future work should incorporate the specific aerosol types emitted during BB events and their aging processes.
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Status: open (until 05 Jun 2025)
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RC1: 'Comment on egusphere-2025-1223', Anonymous Referee #1, 17 May 2025
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Review of Broda et al., 2025
In this paper the authors propose a new method for attributing biomass burning (BB) aerosol optical depth (AOD) values over Warsaw Poland to various global fire source regions. The new method proposed in this paper uses HYSPLIT trajectories, FLAMBE emissions, CAMS GFAS plume rise and NAAPS AOD to derive BB AOD contribution percentages. The authors found that Canada and the US combined contribute a majority of Warsaw’s BB AOD over the fire seasons between 2002-2022. They also determined that European sources of BB AOD are on the decline, compensated by a rise in North American sources of BB AOD (both trends with small, but not statistically significant p-values).
Based on previous research presented in the manuscript’s introduction, it makes sense to focus attribution efforts on Warsaw because attribution studies in this region are scarce. The authors conclusions, for instance regarding which smoke source regions impact Poland and how plume rise plays a role in smoke attribution, seem logical and consistent with the state of the art. I also really liked the trend analysis! However, the manuscript’s methods section has several unclear points and was quite difficult to follow. Since the authors sell the attribution method as the main innovation, the methods section needs to be made much clearer for this paper to be accepted.
Therefore, I recommend the paper be returned to the authors with the following major revisions.
- Methods: this section would greatly benefit from a schematic or a workflow diagram summarizing the 7 steps, including which datasets/models are used at each step. I would also recommend that the authors mention before going into the 7 steps that the overall goal of the methodology is to partition the BB AOD according to emissions encountered from different source regions. There are also some ill-defined terms in the methods section, and I have done my best to point these out.
- Preparatory work: It makes sense to use the forward trajectories to understand which air parcels originating over fire regions are likely to travel to Poland. How were the specific regions selected for trajectory analysis (colored shapes in Fig 1a) selected? Perhaps a map of the probability of plumes reaching Poland would be useful here. As is, the presented trajectories appear to be somewhat cherrypicked.
- Line 136: please move figure 7 to the first figure discussed, to orient the readers to the source regions of interest.
- Step 1, Line 150: are backward trajectories initialized over Poland/Warsaw?
- Step 2-3: The trajectory length and dispersion area computations are well-defined.
- Step 4: The discussion of fire outbreaks and emissions accounting is very unclear. What does “source region” mean in line 177? Won’t the No Threshold and PBL method count the same emissions multiple times? Please clarify this.
- Step 5: it might make sense to refer to “each method” as “each emissions method” or something similar.
- Step 6: What does “specific region” mean in line 202?
- Step 7: make it clear that the contribution is a percentage. What does “BB AOD across mean”?
- Alaska: Why was Alaska not included as a potential region impacting Warsaw BB AOD? The authors note that lofted plumes have a 1% chance of reaching Warsaw, which seems at odds with their threshold of excluding plumes which have a <0.5% chance of reaching Warsaw.
- Figures: throughout the manuscript there are figures with monthly or regional subplot maps. My recommendation is to add subplot titles identifying the plotted month or region. I would also recommend moving tables 1 and 2 to the supplement and presenting this information in Figure 11 instead.
Citation: https://doi.org/10.5194/egusphere-2025-1223-RC1 - Methods: this section would greatly benefit from a schematic or a workflow diagram summarizing the 7 steps, including which datasets/models are used at each step. I would also recommend that the authors mention before going into the 7 steps that the overall goal of the methodology is to partition the BB AOD according to emissions encountered from different source regions. There are also some ill-defined terms in the methods section, and I have done my best to point these out.
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