the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Aug 2024
HTAP3 Fires: Towards a multi-model, multi-pollutant study of fire impacts
Abstract. Open biomass burning has major impacts globally and regionally on atmospheric composition. Fire emissions include particulate matter, tropospheric ozone precursors, greenhouse gases, as well as persistent organic pollutants, mercury and other metals. Fire frequency, intensity, duration, and location are changing as the climate warms, and modelling these fires and their impacts is becoming more and more critical to inform climate adaptation and mitigation, as well as land management. Indeed, the air pollution from fires can reverse the progress made by emission controls on industry and transportation. At the same time, nearly all aspects of fire modelling – such as emissions, plume injection height, long-range transport, and plume chemistry – are highly uncertain. This paper outlines a multi-model, multi-pollutant, multi-regional study to improve the understanding of the uncertainties and variability in fire atmospheric science, models, and fires’ impacts, in addition to providing quantitative estimates of the air pollution and radiative impacts of biomass burning. Coordinated under the auspices of the Task Force on Hemispheric Transport of Air Pollution, the international atmospheric modelling and fire science communities are working towards the common goal of improving global fire modelling and using this multi-model experiment to provide estimates of fire pollution for impact studies. This paper outlines the research needs, opportunities, and options for the fire-focused multi-model experiments and provides guidance for these modelling experiments, outputs, and analysis that are to be pursued over the next 3 to 5 years. It proposes a plan for delivering specific products at key points over this period to meet important milestones relevant to science and policy audiences.
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CEC1: 'Comment on gmd-2024-126', Astrid Kerkweg, 06 Sep 2024
Dear authors,
please note, that also for "model experiment description papers" at least a data availability section is applicable. Usually, the information of the input data used for the experiments is put there. However, I see, that you keep it very open on what input (e.g. emissions) could be used.
However, the data availability section should provide the link, where to find the data. Therefore. at least provide some text refering to the respective sections providing information on the input data.
Yours, Astrid Kerkweg (GMD Executive Editor)
Citation: https://doi.org/10.5194/gmd-2024-126-CEC1 -
AC1: 'Reply on CEC1', Cynthia Whaley, 09 Oct 2024
Thank you for this guidance. When we submit a revised manuscript, we will include the following information in the Data Availability section, as well as adding the associated data set references for each to the reference section. Note at this time that 2 of the 5 datasets are finalized, and the other 3 will be finalized in the next month or so.
- The anthropogenic emissions files for the historical period are available here: https://edgar.jrc.ec.europa.eu/dataset_htap_v3 (NOTE: this will be updated shortly for HTAPv3.1 that we actually recommend using).
- The anthropogenic emissions files for the future period are available here: https://zenodo.org/records/10366132
- The biomass burning emissions for the historical period are available here: https://zenodo.org/records/13753452?preview=1&token=eyJhbGciOiJIUzUxMiJ9.eyJpZCI6Ijg5YzQwNDAzLTI4N2MtNDVhYi05MDU3LTk0ODIxYzc3MDgzYyIsImRhdGEiOnt9LCJyYW5kb20iOiJlMWE5YTI1M2NkOTk0ZWM2M2M1ZTE2NjNiMjBkNTBkZSJ9.VE-ixPpsUTPVQHpCbI7ZaqnlrVB963MmQw3Ly3czYozhRqy3wU1DCEjcNxGvqQ-1ImX7uyLSNfBy0d6KFjG5Lg (NOTE: this is a beta version of the NILU-GFASv1.2.1 that may be updated in the near future after community feedback).
- And the biomass burning emissions for the future period are available here: (NOTE: these will be uploaded at Zenodo and link to be provided in the near future).
- The ERA5 reanalysis recommended for meteorology is available here: https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=form
Citation: https://doi.org/10.5194/gmd-2024-126-AC1 - The anthropogenic emissions files for the historical period are available here: https://edgar.jrc.ec.europa.eu/dataset_htap_v3 (NOTE: this will be updated shortly for HTAPv3.1 that we actually recommend using).
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AC1: 'Reply on CEC1', Cynthia Whaley, 09 Oct 2024
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RC1: 'Comment on gmd-2024-126', Anonymous Referee #1, 10 Oct 2024
This paper presents a proposed protocol for a new set of HTAP experiments, focused on biomass burning. This paper is overall well written and provides a comprehensive description of the protocol. I have however a number of points and questions that would warrant being clarified.
Line 118: What aspect of uncertainty is being tested here? Most likely just structural uncertainty since initial conditions are not really considered in the protocol
Line 120: Isn’t there a risk that this pushes towards a parameter optimization? Isn’t it more important to be right for the right reasons?
Line 210: Critical in what aspect?
Line 260: I am not sure “congener” is the right term here
Line 284: That is true that isotopic measurements might shed some light in this question of fingerprinting. However, on the modeling side, it seems to me that there might be ways of using tagging methods to isolate specific contributions. It would not work with all tracers, but should work with some, especially within a few days of transport/chemistry from emissions.
Line 334 and Table 1: RF is usually estimated as the change in radiative fluxes with respect to a reference period/composition. What is the reference here? No biomass burning? Are those Instantaneous radiative forcing calculations?
Lines 482-484: the sentence does not quite make sense
Lines 492-497: The use of those scenarios continues to make a comparison with CMIP difficult. And it is noted later in this paper the importance of connection with AerChemMIP2. What is the justification for using those scenarios?
Lines 500-504: what is the rationale for not harmonizing? This seems like a serious oversight that makes the comparison of the two simulations much less meaningful
Line 565: In that section, should there be a discussion of the potential emission of micro-plastics?
Section 4.3.2.: this is just a description of CMIP6. How does that apply to the protocol discussed here?
Figure 3: it seems to me that a region prone to very large fires such as the Mediterranean basin should have a box by itself. What is the rationale for such generic areas (other than the fact that’s the way it’s done for other HTAP projects)?
Line 747: how long are the simulations intended to be?
Figure 4: the color scheme makes it hard to identify the SAOM areas.
Line 758: this is an awkward sentence.
Line 821: the only thing that these experiments will do is to show how sensitive the results are to deposition. Will there be an attempt to use deposition data where available?
Lines 843-845: the use of 4 years is better than a single one, but there is then the covariance of fire and meteorology. One could tease out the separate roles by keeping one constant, in addition of having them both vary.
Line 931: how are the “radiative forcing output for climate impacts” computed? Are those from a double call to the radiation?
Section 5.5.2: will that take into account potential changes in population size and age distribution for the future simulations? Some analysis have shown that this was the largest factor (e.g. https://www.nature.com/articles/s41893-022-00976-8)
Citation: https://doi.org/10.5194/gmd-2024-126-RC1 -
RC2: 'Comment on gmd-2024-126', Anonymous Referee #2, 27 Nov 2024
General Comments
The authors describe the motivation, scope, and experimental design of a planned multi-model, multi-scale, and multi-pollutant study that is aimed at improving our understanding of wildland fires and their impacts on air quality. The planned work under HTAP3 Fires is indeed a very worthwhile endeavor, and sections 2 and 3 of the manuscript provide an excellent summary of the research needs and how the expected results of this effort can help address important science and policy questions. While sections 4 and 5 are intended to provide details on how the planned activity will be conducted, reading these sections created the impression that some aspects of the study are still fluid and may be decided at a later time. Several instances of such ambiguities between firm plans vs. potential avenues for research are noted in my detailed comments below and should be clarified in the revision. While I appreciate the benefit of publishing an experimental design paper now to anchor the activity, the drawback of this early publication is that a fair amount of information which would ordinarily belong in an experimental design paper (e.g. a definitive list of selected – rather than potential - case studies, protocols for coordinating modeling and analyses across global and regional scales, infrastructure for model evaluation) are not yet finalized, thereby limiting the utility of this paper as a definitive reference for the planned work. This doesn’t argue against publishing the manuscript at this stage, but should be acknowledged in the discussion. In general, I find that the expansive scope of the HTAP3 Fires modeling activity, as outlined in this paper, is a great strength but could also pose challenges when it comes to analyzing, synthesizing, and interpreting the results. I am certainly looking forward to these results and wish the organizers and participants of the activity best of success.
Specific Comments
Line 67: “analyses” instead of “analysis”?
Line 73: remove the comma after the semicolon
Line 128: please clarify what is meant by “differ based on initial pollutant focus”
Lines 160 – 162: This reads like a repeat of the discussion for chemistry in freshly emitted plumes on lines 152 – 153
Line 227: remove “, which” between “(POPs)” and “are synthetic pollutants”
Lines 294 – 295: Does the Xu et al. (2023) study also refer to worldwide numbers, like the Johnston et al. (2012) study referenced in the previous sentence?
Lines 321 – 322: This sentence needs rewording, starting with “’is highly uncertain” which is a phrase used at both the beginning and end of this portion of the sentence.
Lines 334 – 326: Please revisit the structure of these two sentences: “Though, most studies focus on … only. However, …”. Maybe remove “though” at the beginning of the first sentence?
Line 340: Insert “source of” before cloud condensation nuclei?
Line 349: Please define rBC
Lines 349 – 350: It is unclear what the last part of the sentence “might help to reduce these discrepancies between the models” refers to – new measurement data? If so, consider breaking this into a new sentence, after “Dobracki et al., 2023)”. “In addition, new data might also help to …”
Lines 356 – 357: “Note that for some regions, actions have been taken to reduce such impacts which may or may not be accounted for or represented well in models.” – which types of models does this refer to? As written, it’s a rather vague statement.
Line 421: Suggest not referring to HCHO as a by-product of SOA, given that it is also emitted as well as produced as part of the atmospheric oxidation of isoprene and monoterpenes.
Lines 445 – 447: Suggest also mentioning chemistry transport models that ingest meteorology from prognostic meteorological models employing nudging– the current description would seem to cover models like WRF/Chem or GEM-MACH with the first example, and models like GEOS-Chem with the second example, but not modeling systems like WRF-Chimere where WRF simulations (employing nudging towards reanalysis fields) are used as input to Chimere.
Line 480: Based on my reading of Section 2.3.2 of Crippa et al., it is not correct to refer to the U.S. portion of HTAPv3 as “official national inventories”. Instead, these emissions were based on the EPA’s Air QUAlity TimE Series Project (EQUATES), as described in Foley et al. (2023) (https://doi.org/10.1016/j.dib.2023.109022). As discussed in Crippa et al., “For each sector, a consistent methodology was used to estimate emissions for each year in the 16-year period, in contrast to the evolving methodologies applied in the triennial US National Emissions Inventories (NEIs) produced over that span.”
Line 485: “By September 2024, HTAP v3.1 …” To my knowledge, these emissions were not released in September 2024. Please update the timeline.
Line 491: “will be available from July 2024”. To my knowledge, these emissions were not released in July 2024. Please update the timeline.
Line 505: is there no plan to apply CTMs with historic meteorology for future emission scenarios?
Lines 506 – 510: This section also needs to discuss how individual models will speciate VOC and PM2.5 emissions into their gas phase chemistry and aerosol mechanisms. Will reference speciation profiles be provided, or will this important decision be up to each group? How do the HTAPv3 (and GFAS) emissions handle intermediate-volatility organic compounds (e.g. https://acp.copernicus.org/articles/19/8141/2019/, https://doi.org/10.1016/j.oneear.2022.03.015, https://acp.copernicus.org/articles/23/13469/2023/, and references therein)? If these are not fully accounted for in the emission inventories, can groups account for such missing mass in their simulations by applying correction factors?
Lines 512 – 513: Please provide a reference for each of these inventories.
Lines 517 – 518: Does this statement refer to the workshop discussions, the studies listed on lines 515 – 516, or both? Will FIRECAM be used in this study? If not, what is the motivation for mentioning it here?
Line 519, Table 2: This table should include all of the latest available major fire emission datasets listed at the beginning of Section 4.2.2. In addition, FEERv1.0-G1.2 is shown in the table but not named as one of the major fire emission datasets listed at the beginning of Section 4.2.2.
Lines 538 – 539: Why is GFAS (v1.4) mentioned here – are there plans for using it in later stages of HTAP3 Fires? If not, what is the relevance of mentioning it?
Line 544 as well as Table 2: Please define FRP upon first usage. Right now, it is not defined until about line 750.
Lines 546 - 548: It’s not clear how the discussion of diurnal FRP information in GFASv1.4 is relevant to this project.
Line 616: “but could be corrected to GFASv1.2” – is this a firm plan, or just a possibility? If it’s only a possibility, what is the timeline and decision making process for determining whether this will done?
Lines 632 – 634: please double check the sentence structure following “across a wide range of scales”. Usually “from turbulent mixing …” would be followed by “to …”, but this is not the case here.
Lines 634 – 636: please see my earlier comment on offline CTMs, which do not generate their own meteorology, but are not (directly) driven by reanalysis products, either, instead using meteorological fields from models like WRF that employ nudging.
Lines 638 – 641: Will the choice be completely up to individual modeling groups?
Lines 666 – 667: Satellite data products should not be referred to as direct observations, given that assumptions are invoked when generating such products. Please also discuss how such products will be used in planned evaluation studies and to which extent such analyses will be qualitative vs. quantitative.
Lines 668 – 669: Please provide a list of LIDAR stations and available measurements time periods that will be used in this study.
Lines 669 – 671: “All surface monitoring measurements of the pollutants in Section 3.1 could be used for model evaluation” – it is unclear what “could” means in this context. Will HTAP3 Fires model evaluation activities make use of all such measurements? If so, “are expected” instead of “could” might be a better wording. Also, why does Table S1 list BC and CO surface monitoring data from EMEP over Europe but not corresponding data from NAPS and AQS over Canada and the US? AERONET data also likely would be very useful for this model evaluation activity.
Line 671: change “suggestion” to “suggested”
Lines 681 – 684: The wording “can be used” leaves it unclear whether such cross-disciplinary satellite and in-situ data deposition analyses will be performed as part of HTAP3-Fires. If there are such plans for evaluating deposition, more details are needed on which types of models and modeling periods such an approach would be most applicable for and how it will be implemented.
Lines 685 – 690: This paragraph does not seem to directly relate to how observational data will be used for model evaluation.
Lines 702 – 703: Preferably, an experimental design description paper like this one would have such key decisions already settled when written and submitted. Given that this sentence suggests that this aspect is still in flux, more details are needed on which criteria will be used to determine that reliable emission assessments are available that support the selection of specific time period(s). Time period(s) when relevant observations are available should already be known.
Lines 705 – 710: When will this identification of short-term case studies to be analyzed in HTAP3 Fires be made? What is the process for selecting specific case studies?
Lines 711 – 736. The definition of regions to be used for the perturbation experiments is critical to the design of the modeling study described in this paper. This section provides an unclear message about whether the process for defining these regions is still ongoing (e.g. “these [HTAP2] source regions should be further defined”, “proposed merged regions”) or whether the 8 merged GFED regions shown in Figure 3d already reflect the final definition of regions that will be used. Preferably, it is the latter, in which case the wording in the paragraph should be revised to reflect that Figures 3a – 3c present different potential starting points while Figure 3d shows the final decision, arrived at after making the considerations described in this paragraph. If the region definition process is still in progress, this needs to be clearly stated and would be a fairly major limitation of publishing this experimental design paper now rather than later when such a key decision has been finalized.
Line 758 - 759: The different parts of this sentence don’t quite mesh together, consider revising maybe along these lines: “Much of the uncertainty in the wider impacts of fires arises from weakness in our understanding of fire processes, their representation in models, and the sensitivity of the impacts to these treatments”
Line 768: Rather than being “less efficient” in the free troposphere than the boundary layer, dry deposition only occurs at the surface, not the free troposphere.
Line 774: remove comma after “whereas”
Lines 774 – 776: “Daily information on wildfire injection heights … can be used in the calculation of injection heights”. This is unclear – if daily information on injection heights is available, why do they need to be calculated?
Line 780: change “these models” to “the models”
Line 789: Please specify what type of data from these platforms would be used for evaluating the effects of plume rise, whether such evaluation would be quantitative or qualitative in nature, and which time and space scales it would be performed for.
Lines 802 – 808: building upon the third factor listed here, the study might also want to specifically explore how the use of different chemical mechanisms and aerosol schemes affects simulated impacts, holding all other aspects constant.
Line 823: remove “to” before “turn”
Line 830: suggest changing the first occurrence of “provided” to “if” (or “when”, as applicable)
Line 842: remove comma after scales
Line 853, Table 3: Should the future medium option list 2010 – 2020 and 2045 – 2055, instead of 2015 – 2015? The discussion in the text mentions two ten year periods
Line 873: please update the timeline for the release of these emissions
Table 4: The biogenic and other natural emissions section list “MEGAN or models’ own”, but the text says “we suggest that each modeling centre use their preferred emissions from biogenic and other natural sources”. This makes it unclear whether a reference MEGAN dataset (driven by which reanalysis / future meteorology?) will be provided to groups who would like to use it, or if there is no common fallback dataset.
Table 4: The notes/references under historical fire emissions state “Note: these will be updated in the near future to include newer emission factors”. Has this happened already? If not, when will it happen, and are groups expected to use the files with the newer emission factors?
Table 4: The timeline for the historical anthropogenic emissions in the notes/references section is outdated, please update. Please also change “TBD” to the actual download location, it is critical that this information is available before the paper is published.
Section 890 – 894: see my earlier comments about also discussing models that use meteorology by models like WRF, nudged towards reanalysis fields. What is the recommended protocol for these types of models?
Section 5.3 / Table 5 / description of experiments: more detail is needed about the plans for exp2 (case studies) and exp8 (data assimilation)
Section 5.3.1, lines 911 – 919: I suggest also considering perturbations to VOC speciation and the volatility distribution of total emitted reactive organic carbon
Lines 917 – 919: what is the “base” temporal resolution of fire emissions in exp1 – hourly, daily?
Line 946: This should be Table S1, not S0. Also see my earlier comment regarding the availability of CO, BC, and a range of other gaseous and aerosol pollutants from NAPS and AQS. How will the AGES dataset be used since 2023 is not included in the medium or long simulation period options? Will modeling 2023 be required for models conducting “short” case study simulations?
Lines 945 – 954: Will the datasets listed in Table S1 be curated by HTAP3 Fires to provide a common set of variable names, units, metadata, and method and sampling interval information to participants performing model evaluation, or will participants be expected to obtain the raw data from all the different sources listed in Table S1 themselves and then prepare them for model evaluation? Are the community tools listed in this section set up to easily ingest all of the different observational datasets listed in Table S1? More generally, model evaluation is a key component of this activity, and the authors are correct in stating that it will require a large effort by the community. It would be good if this paper could provide a clearer roadmap for how this critical model evaluation task will be accomplished as part of HTAP3 Fires, including the creation of infrastructure for obtaining and harmonizing observations and outlining how meaningful evaluation efforts will be structured given the diversity of models and temporal and spatial scales of the expected model outputs. This roadmap should also include discussion whether the HTAP3 Fires organizers expect to provide leadership on model evaluation or whether this will entirely rely on community volunteers.
Lines 964-965: please define “high spatial and temporal resolution” and discuss what resolution is needed for such novel health risk assessments, as this will inform the required design of model simulations. Please also discuss how these anticipated health risk assessments would account for model biases, e.g. by employing data fusion or other bias correction techniques, and provide details on such planned analyses.
Lines 966 – 971, section 5.3.3: This section lacks specificity of the planned analyses.
Citation: https://doi.org/10.5194/gmd-2024-126-RC2
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