the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
04 Jan 2021
04 Jan 2021
Opinion: Papers that shaped Tropospheric Chemistry
- 1School of Chemistry, University of Leicester, University Rd., Leicester, LE1 7RH, UK
- 2Colorado State University, Fort Collins, Colorado, USA
- 3Institute for Advanced Sustainability Studies, Berlinerstrasse 130, 14467 Potsdam, Germany
- 1School of Chemistry, University of Leicester, University Rd., Leicester, LE1 7RH, UK
- 2Colorado State University, Fort Collins, Colorado, USA
- 3Institute for Advanced Sustainability Studies, Berlinerstrasse 130, 14467 Potsdam, Germany
Abstract. Which published papers have transformed our understanding of the chemical processes in the troposphere, and shaped the field of atmospheric chemistry? By way of expert solicitation and interactive peer-review, this paper explores the influence of the ideas in peer-reviewed articles based on the input from our community of atmospheric scientists. We explore how these papers have shaped the development of the field of atmospheric chemistry, and identify the major landmarks in the field of atmospheric chemistry through the lens of those papers' impact on science, legislation and environmental events. We also explore the ways in which one can identify the papers that have most impacted the field and discuss the advantages and disadvantages of the various approaches.
Paul S. Monks et al.
Status: closed
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CC1: 'Comment on acp-2020-1266', Joel Savarino, 05 Jan 2021
Dear authors
thank you for gathering this corpus of founding articles to understand the construction, evolution and fundamental discoveries of this discipline that is the chemistry of the atmosphere. This article will remain a reference and an entry point for the new generation of researchers, as well as for the older generation to understand its field and progress.
As indicated at the end of the article, I would like to provide additional information. It seems to me that Lovelock's article (1) and his discovery of DMS (thanks to his invention of the ECD detector (2) which also allowed the first measurements of CFCs) as the reduced sulfur compound emitted by themarine biota(and not H2S as thought previously) would have its place in this article. This article also advances the idea that the MSA resulting from the oxidation of DMS is a probable source of aerosols. It is on the basis of this article that the CLAW hypothesis was born. This article deserves to be mentioned.
In the same vein, I think Patterson's paper on the increase of lead in the air (3) (actually in snow) as well as its decrease since the elimination of lead in gasoline (4) would be worth mentioning. With the elimination of CFCs, this is the other major victory of atmospheric chemistry research over environmental policy.
With regards
1- Lovelock, J. E., Maggs, R. J., and Rasmussen, R. A.: Atmospheric Dimethyl Sulphide and the Natural Sulphur Cycle, Nature, 237, 452-453, 10.1038/237452a0, 1972.2- Lovelock, J. E., SR Lipsky,Electron Affinity Spectroscopy-A New Method for the Identification of Functional Groups in Chemical Compounds Separated by Gas Chromatography -Journal of the American Chemical, 82, 431, 1960.
3-Murozumi, M., Chow, T. J., and Patterson, C. (2003): Chemical concentrations of pollutant lead aerosols, terrestrial dusts and sea salts in Greenland and Antarctic snow strata, Geochim. Cosmochim. Acta, 33, 1247-1294, https://doi.org/10.1016/0016-7037(69)90045-3, 1969.
4-Boutron, C. F., Görlach, U., Candelone, J.-P., Bolshov, M. A., and Delmas, R. J.: Decrease in anthropogenic lead, cadmium and zinc in Greenland snows since the late 1960s, Nature, 353, 153-156, 10.1038/353153a0, 1991.
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AC10: 'Reply on CC1', Paul Monks, 28 Jun 2021
Thank-you for the comments. With respect to the Lovelock ECD work, the reference and description has been added to the VOC section. The extra information on the MSA/DMA Lovelock work has been added to the description of CLAW hypothesis. Further, a small section on lead including the suggested works have been added to the foundations section.
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AC10: 'Reply on CC1', Paul Monks, 28 Jun 2021
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CC2: 'Comment on acp-2020-1266', Pawan Gupta, 05 Jan 2021
Page 35, Section 2.17 - "A step-change in this area was made with the paper “Estimating 929 ground-level PM2.5 using aerosol optical depth determined from satellite remote sensing” by van Donkelaar et al. (2006) which was the first description of the derivation of surface PM2.5 from satellite AOD, and which has been extensively used to estimate the global impact of particulate matter (both PM2.5 and PM10) on health"
It appears that the above assessment is not correct.
The first paper showing quantitative PM2.5 estimation using satellite AOD was published in 2003 as 'Wang, J., and S. A. Christopher, Intercomparison between satellite-derived aerosol optical thickness and PM2.5 mass: Implications for air quality studies, Geophys. Res. Lett., 30(21), 2095, doi:10.1029/2003GL018174, 2003'
introduced a simple statistical method to estimate PM2.5 using satellite data, later on, the following paper by Liu et al., (2004)
"Liu, Y., Park, R. J., Jacob, D. J., Li, Q., Kilaru, V., and Sarnat, J. A. (2004), Mapping annual mean ground‐level PM2.5 concentrations using Multiangle Imaging Spectroradiometer aerosol optical thickness over the contiguous United States, J. Geophys. Res., 109, D22206, doi:."
first introduced the model scaling approach, which was later adopted by van Donkelaar et al. (2006) and resulted in global estimates of PM2.5 at annual mean levels.
Over the last two decades, there have been several hundreds of papers published in assessing the satellite-derived AODs to estimate surface particulate matter air quality.
- AC8: 'Reply on CC2', Paul Monks, 28 Jun 2021
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CC3: 'Comment on acp-2020-1266', Viney Aneja, 05 Jan 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-CC3-supplement.pdf
- AC3: 'Reply on CC3', Paul Monks, 28 Jun 2021
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CC4: 'Comment on acp-2020-1266', Sandro Fuzzi, 07 Jan 2021
I want to congratulate the authors for putting together this interesting overview based on a series of suggestions from the science community.
In the spirit of collaboration that the authors ask for, I have a few comments.
- AC16: 'Reply on CC4', Paul Monks, 28 Jun 2021
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CC5: 'Comment on acp-2020-1266', Sandro Fuzzi, 08 Jan 2021
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AC15: 'Reply on CC5', Paul Monks, 28 Jun 2021
With respect to the comparison in Table 1 (revised version, Table 2 in submitted version), we felt it useful to highlight the differences and also shortcomings of a solely metric approach (as highlighted in the text). The difference remarked on is the very essence of the problem.
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AC15: 'Reply on CC5', Paul Monks, 28 Jun 2021
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CC6: 'Comment on acp-2020-1266', Sandro Fuzzi, 08 Jan 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-CC6-supplement.pdf
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AC7: 'Reply on CC6', Paul Monks, 28 Jun 2021
We did consider this idea "Appendix 1 shows very interesting results on journalsand regions of the references reported in the paper. I would suggest to include an Appendix 2 reported similar statistics concerning the contributions received by the authors from the call through the IGAC community." but for two reasons decided not to do it. The first was to avoid the top 10 lists mentality and the second was with just over 50 contributors the statistics where not robust.
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AC7: 'Reply on CC6', Paul Monks, 28 Jun 2021
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CC7: 'Comment on acp-2020-1266', Nick Hewitt, 14 Jan 2021
Thanks for this excellent overview of atmopheric chemistry research. It made really interesting reading.
I have a suggestion to make about section 2.13 on biogenic VOCs. Please see the linked document.
- AC4: 'Reply on CC7', Paul Monks, 28 Jun 2021
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CC8: 'Comment on acp-2020-1266', David Griffith, 15 Jan 2021
Dear Paul, Ravi et al.,
Thank you for the considerable effort in putting this history together – to one active in the field since the late 1970s (when the curve in Fig 1 kicks off), it is an enjoyable read, and a trip down memory lane.
Inevitably, having solicited them, you will get lots of suggestions for things that you have left out or rated less important than judged by others. Already there are several… So I will add mine, for your consideration. Two areas in my view deserve their own explicit subsection of section 2. Some aspects are already mentioned in passing in several places, but my judgement would be that they deserved their own explicit subsection.
- Measurement techniques. We might divide up the whole topic into two sub topics – the chemistry itself, and the methods used to probe it. Many advances in our understanding of atmospheric chemistry have come from stepwise advances in measurement (and modelling) capabilities. There are already explicit sections for kinetics, models, meteorology and transport and satellite measurements, but nothing explicitly for chemical measurement techniques. The success of the high impact journal AMT speaks for the importance. Examples of discoveries that might be included in this area might be (but are not limited to):
- The ECD detector (Lovelock), which enabled the detection of halocarbons
- PTR-MS – already mentioned in 2.12 in the VOC context
- OH measurements – LIF etc.
- The chemiluminescence technique for NO and NOx
- Dobson method for O3 (admittedly stratospheric)
- Satellite retrievals – satellite global mapping of composition has been a real revolution.
- Greenhouse and climate-relevant gases (and aerosols). Given the current state and importance of climate change science and policy, a separate section on greenhouse and other climate-relevant species seems to me to be very desirable. There are some mentions throughout, eg to Keeling and to long term monitoring networks like ALE/AGAGE. GAW, NOAA, ICOS, but it would be valuable to bring them together into their own section. Also the techniques that enable reliable and accurate long term records to be maintained – NDIR, optical in situ and remote sensing techniques, isotopic methods, and satellite measurements (again).
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AC12: 'Reply on CC8', Paul Monks, 28 Jun 2021
Thank you for the comments, in respect of
1. Measurement techniques
1. The ECD detector (Lovelock), which enabled the detection of halocarbons Reference to the Lovelock work on ECD added to VOC section 2. PTR-MS – already mentioned in 2.12 in the VOC context PTR-MS discussed in section 2.12 3. OH measurements – LIF etc. References and discussion added, on instrumentation and OH measurement 4. The chemiluminescence technique for NO and NOx Reference to original work from Kley and McFadden added 5. Dobson method for O3 (admittedly stratospheric) Added full historical context of stratospheric ozone 6. Satellite retrievals – satellite global mapping of composition has been a real revolution. The section on satellite measurements reflects this. 2. Greenhouse and climate-relevant gases (and aerosols) - The long-term measurements of GHG and other climate relevant gases was missing. A small section highlighting some of the main measurement networks has been added, plus additional information on the value of long-term measurements.
- Measurement techniques. We might divide up the whole topic into two sub topics – the chemistry itself, and the methods used to probe it. Many advances in our understanding of atmospheric chemistry have come from stepwise advances in measurement (and modelling) capabilities. There are already explicit sections for kinetics, models, meteorology and transport and satellite measurements, but nothing explicitly for chemical measurement techniques. The success of the high impact journal AMT speaks for the importance. Examples of discoveries that might be included in this area might be (but are not limited to):
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RC1: 'Comment on acp-2020-1266', Anonymous Referee #1, 18 Jan 2021
This is a wonderful paper that will provide many future generations of atmospheric scientists some perspective on how the field developed and its current status. The limitations and approach taken are clearly stated and their emphasis on integrating all aspects of the field, ambient measurements, lab studies and modeling, is terrific.
This reviewer has just a few suggestions and minor typo's etc.
- Line 34: Suggest adding at least one other review from the health community re: human health impacts, e.g. by Landrigan et al in Lancet, 2018. The introduction says it is only treating papers 2010 and earlier but cites a 2015 Lelieveld paper for health effects so I assume later papers than 2010 are being cited for background?
- Throughout, the word "aerosols" is used to denote "particles". Historically, the engineers who developed much of this area and the instrumentation have defined aerosols as particles and the gas in which they are suspended (e.g. see Hinds book). This would be a good place to exhibit consistency and use "aerosol particles" throughout, or just "particles" if that is what they mean.
- Line 360: As the authors indicate in the introduction, the fundamental work on which significant advances are made often ends up not being cited as the field develops. The laser ionization MS technique I think originated with Sinha, Rev. Sci. Instrum. (1984), followed by papers coauthored with Friedlander. It might be appropriate to include one of these references along with Prather and Murphy.
- Line 367: I would add for clarity at the end of the sentence on this line "that assumed low viscosity, liquid-like particles where exchange with the gas phase is fast".
- Line 445: They state that the "distinction between heterogenous and multiphase chemistry is not always clear". This would be a good place to define these terms.
- Lines 453-469: These two paragraphs mix multiphase and heterogenous chemistry in a somewhat random order. I think they are using "heterogeneous" to mean reactions at surfaces and "multiphase" to mean reactions involving the uptake of gases into (and reaction in) the liquid phase. It would be good to define the terms first and then separate out the examples they give into the two bins.
- Line 455-459: This cites the work of Akimoto et al on the photoenhancement of HONO formation but it seems some discussion of the dark formation of HONO should come first. The Pitts et al, Int. J. Chem. Kin. (1984) might be the first discussion of this in chambers. Finlayson-Pitts et al, PCCP (2003) is a review of the area to that point.
- Lines 571-573: It reads as if Sillman (1999) was the first to put together ozone isopleths but this goes back into the 1950's or 60's, probably Haagen-Smit and Fox (1954). It would be good to cite the origins here as it is so important to our understanding even today.
- Lines 685-692: Shroeder and Urone (EST, 1974) were probably the first to suggest sea salt reactions as a photochemical source of chlorine atoms. It could be cited here and on line 704. A review by Cicerone in Rev. Geophys. Space Phys. (1981) would be a good review too.
- Line 846: It seems odd to state that emission inventories were pioneered in the 1990's. Surely they were being developed long before that, at least in California?
- Lines 925-927: Satellites have been really useful for tracking dust events but it seems that either here or in another section a reference to the seminal studies on dust transport of Prospero et al in the 1970's should be included.
- Line 988: "by now phased out the ozone-depleting gases". I think this is overly optimistic to say this, given recent measurements showing there seem to be emissions from Asia that were not expected. Maybe "are now phasing out ozone-depleting gases"...
- Table 1 seems quite Euro-centric, for example not including some of the big smog events in the U.S. and the passage of the Clean Air Act etc.
- Table 2 is in two parts. It was not clear to this reviewer how they differ from each other in what they are supposed to illustrate.
- Table 3 seems out of context. It is very detailed on NOx but similar detail is not given for other species. I suggest omitting this.
- Appendix 1 data go to 2020. Since the focus of the article is 2010 and prior years, some comment in the captions might be appropriate.
Minor typos, grammar etc:
- Line 34: impacts.
- Line 35: "latterly links to their climate" is very awkward. Maybe replace "latterly links to their climate" with "and climate"
3.Line 178: "pollutions"
- Line 626: "any" should be "many"?
- Line 824: "..most cited paper"
- Line 885: Should "The study" be omitted so the sentence starts: "Moody et al (1998) ..."
- Line 900: Spelling error "emmited"
- The formatting of the references (no space between etc) makes them very hard to read but I suppose that will get straightened out in the final document.
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AC2: 'Reply on RC1', Paul Monks, 28 Jun 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-AC2-supplement.pdf
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CC9: 'Comment on Emission and Deposition', Thomas Karl, 21 Jan 2021
This is an excellent and broad perspective on tropospheric chemistry. As such it will certainly become a valuable reference and resource. As already pointed out by Nick Hewitt, it was actually Sanadze who first reported substantial isoprene emissions from plants in Russia (1957). Rasmussen independently found similar results in the US. I highly recommend the review article by Sharkey and Monson on 60 years of isoprene research. (Isoprene research – 60 years later, the biology is still enigmatic, doi: 10.1111/pce.12930, 2017). Further it is mentioned that "recent interest in deposition reemerged", but that physio-chemical parameters are lacking. Physio – chemical parameters for most gases (e.g. HLC, vapor pressure, reactivity etc.) are very well established and an important reason why the ‘Wesely scheme’ works quite well for classic air pollutants over many surface types. I would argue that the complication stems more from a range of oxygenated VOC that can exhibit bi-directional exchange above vegetation (e.g. doi: 10.1126/science.1192534, doi: 10.1126/science.1235053). Moreover it was recently demonstrated that plants can also "reprocess" OVOCs, produced during atmospheric oxidation, through enzymatic reactions (doi: 10.1038/s43247-020-00041-2 ). The concept of bi-directional exchange is not included in the theoretical framework of emission and deposition models as there is little need for most gases. Yet, it is somewhat overlooked when discussing the fate of reactive organic carbon as many oxygenated volatile species can reside in this no-man’s land.
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CC11: 'Reply on CC9', Paul O. Wennberg, 19 Feb 2021
Indeed, deposition (and emission) of oxygenated VOCs is an important new frontier.
Nguyen et al., 2015 ( https://www.pnas.org/content/112/5/E392 ) and Wolfe et al., 2015 ( https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL065839 ) evaluated such fluxes against the Wesley scheme and illustrated some of the shortfalls.
- AC6: 'Reply on CC11', Paul Monks, 28 Jun 2021
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AC9: 'Reply on CC9', Paul Monks, 28 Jun 2021
Thank-you for the insightful comments. The correction made as to origin of isoprene and excellent review article from Sharkey and Monson has been added. With respect to the second point around bi-directional fluxes, a senetence and reference has been added to capture this point.
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CC11: 'Reply on CC9', Paul O. Wennberg, 19 Feb 2021
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CC10: 'HONO_Comment on acp-2020-1266', Yasin Elshorbany, 25 Jan 2021
I commend the authors for leading this nice effort and inspired by the call for contributions, I have a few suggestions. I am missing a discussion on nitrous acid (HONO) which has emerged as a major source of OH radical during the last 15 years.
Here is a relevant draft summary:
HONO photolysis is a major OH source, especially during the early morning, which was first identified by Perner and Platt (1979):
HONO + hν (λ < 400nm) → OH + NO
During the daytime, photolysis of HONO has been shown to be the most important OH initiation source under urban high NOx conditions (e.g., Elshorbany et al., 2009a, 2009b) and was found to have a significant impact on ozone photochemical formation (Elshorbany et al., 2010). HONO was also demonstrated to have large global impact on gas phase (Elshorbany et al., 2012) and aerosol formation (Elshorbany et al., 2014).
HONO is now recognized as an important species that is being measured routinely during field measurements. Attempts are currently underway to detect it from space, which is being challenged by its low near-surface concentrations but was recently detected in biomass burning emissions.
HONO research is driven by unexpected high daytime values of HONO (e.g. Neftel et al., 1996, Zhou et al., 2002; Kleffmann et al., 2002; Acker et al., 2006a, 2006b, Elshorbany et al, 2009). Several photochemical HONO sources have been proposed (Kleffmann, 2007), some of which have been identified in the laboratory (e.g., Zhou et al., 2003; George et al., 2005; Stemmler et al., 2006, 2007; Bejan et al., 2006; Li et al., 2008, Gustafsson et al., 2006; Ndour et al., 2008). HONO sources in the atmosphere are not yet well understood. While the dark heterogeneous conversion of NO2 on humid surfaces (Finlayson-Pitts et al., 2003) is commonly accepted as the dominant HONO sources during night (Alicke et al., 2002), the exact mechanism is still unclear:
2 NO2 + H2O → HONO + HNO3
In addition, recent studies showed that the heterogeneous reaction of NO2 with adsorbed hydrocarbons are also important under atmospheric conditions (Ammann, et al., 2005).
NO2 + Organics(red) → HONO + Organics(oxi.)
For HONO daytime sources, five photochemical mechanisms were recently identified. Three of them dominate under high NOx urban conditions, namely heterogeneous conversion of gaseous NO2 on photosensitized solid surface organic compounds (George et al., 2005; Stemmler et al., 2006), photocatalytic conversion of NO2 on TiO2 (Gustafsson et al., 2006; Ndour et al., 2008) and the photolysis of the gaseous nitroaromatic compounds (Bejan et al., 2006) and should correlate well with j(NO2). Under low NOx rural conditions, the photolysis of nitric acid (Zhou et al., 2003) adsorbed on solid surfaces (including vegetations) may dominate and would better correlate to j(O1D), caused by the much lower wavelength range of the nitric acid photolysis.
- AC5: 'Reply on CC10', Paul Monks, 28 Jun 2021
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RC2: 'Comment on acp-2020-1266', Anonymous Referee #2, 03 Feb 2021
Review of the paper by Monks et al entitled “Opinion: Papers that shaped Tropospheric Chemistry”.
This wonderful paper represents a very important contribution because it shows the evolution of an important research field until year 2010. It will provide to the new generations of students and scientists an excellent historical introduction that will allow them to realize how the concepts have evolved and how science progresses. It is particularly interesting to understand that progress in atmospheric chemistry resulted from the complementarity between laboratory experiments, field measurements, data analysis and modeling.
I like the paper very much. I will highlight its strengths but I will also make some suggestions to make the paper somewhat more inclusive. I find the paper a bit unbalanced towards process studies and laboratory work (which should be highlighted as they are) at the expense of field work and modeling.
Strength of the Paper
The paper covers a lot of material and reports a lot of important results that shaped the field of atmospheric chemistry. A lot of bibliographical material is provided. Several graphs and tables are very interesting including, for example, the documents by sources and year and by country. The two tables with the top 10 cited papers are useful.
The grouping of 19 topics presented in Section 1.2 is excellent.
The discussion about how the papers were selected and the limitations to this approach is very good. It shows that the methodology does not provide an absolute standard and that work not included in this list can also be excellent.
The paper is well written and easy to read. I am sure that people starting their career will like to read the document.
Suggestions.
As I said above, I find the paperto be a bit unbalanced towards fundamental processes at the expense of more global and regional investigations. This could be easily addressed by adding some references to a few important observational and modeling accomplishments. Sometimes, big advances related, for example, to filed campaigns are not presented as a single paper, but are dispersed in several papers, and so none of them has a highest citation rate. For example, a major accomplishment before 2010 has been the organization of several airborne campaigns. Not only the ER-2 measurements of the ClO/O3 reactions have been key for the ozone hole question, but also the numerous airborne field campaigns in the 1980’s and 1990’s (many NASA field campaigns) that have provided insight on global tropospheric chemistry, and in particular on questions related to the oxidation capacity of the atmosphere.
A lot has been learned from field campaigns (such as PEM, Trace P, ACE, and several others) and so perhaps, the authors could mention large projects that have provided fundamental understanding of the functioning of the atmosphere at the global and regional scales. Other topics that illustrate major advances:
Field campaigns to assess NOx produced by lightning and the importance of thunderstorms
Production of methane by rice paddies, particularly in Asia
Monitoring of methane and carbon monoxide by international networks
Systematic observations of ozone and CO from commercial aircraft
Perhaps a bit more should be said about space observations. Much progress has been done before year 2010. The measurement of CO from the Space Shuttle gave a first global view of the distribution of this species and highlighted the role of biomass burning, particularly in the tropics. Beside GOME, and SCIAMACHY, one should perhaps refer to other important satellites and instruments such as OMI, MOPITT, MODIS, TES, etc. since they provided again a global view that was very useful to understand global budgets and the role of transport.
Finally, the Section on modeling is a bit weak. Models have been key for the interpretating observations, analyzing the role of chemical processes and projecting future changes in the atmospheric composition. The first relatively detailed 3-D model of the troposphere (although a bit intermediate) were developed in Mainz (MONGUNTIA), in Brussels (IMAGES) and at Livermore (GRANTOUR). They were followed by major efforts to develop really comprehensive chemical transport models (GeosChem at Harvard, MOZART at NCAR, Uni. Of Oslo model, and MESSY in Mainz, CHASER in Japan, etc.
For stratospheric work, which is also mentioned in the paper, 2-D models such as the model of Garcia and Solomon have been a key tool to implement the fundamental concepts of the stratospheric residual circulation (and related meridional transport) resulting from planetary wave breaking presented by Holton and McIntyre, and to assess how the residual circulation could explain the meridional transport of ozone and other tracers in the middle atmosphere. Several 3-D stratospheric models were also developed for the stratosphere. One of the first ones was developed at MIT by Cunnold, Aleya and Prinn and at GFDL by Mahlman. Some more advanced models include WACCM developed at NCAR
Nothing is said about the first attempts to develop inverse modeling techniques and chemical data assimilation methodologies, which were initiated in the late 1990s.
I do not want to provide a “list of what is missing” since the goal of the paper is to highlight bthe most cited papers, but I am making some general points that perhaps would be welcome, and I am not asking to the authors to necessarily including all of them in the text. These are just constructive suggestions.
Some minor remarks on the text
Around line 109: How many responses were provided in response your solicitation of the scientific community?
Line 320; Can you add a reference and perhaps an estimate of the uncertainty about the -1.1 Wm-2 ?
Figure 4 looks dark to me and low quality (it may be my printer).
Lines 364 to 367: Difficult to understand if you are not specialized (amorphous solid state). Beside the fact that it challenged the traditional views, what are the consequences of this discovery?
Line 539: Second or third? I thought that methane was second (and close to ozone).
Figure 10: the figure does not read well. Complicated to understand with such a short caption. Also, on the y-scale, it seems strange to express an integrated flux in ppb. I guess that it is integrated over time, but for how long.
Line 742: I am not sure that research is trying to count the numbers of VOCs present in the atmosphere.
Line 949: It is appropriate to cite Hampson, but a reference to his report should be added.
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AC1: 'Reply on RC2', Paul Monks, 28 Jun 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-AC1-supplement.pdf
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AC1: 'Reply on RC2', Paul Monks, 28 Jun 2021
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CC12: 'Comment on acp-2020-1266', Owen Cooper, 20 Feb 2021
Comment by:
Owen R. Cooper
Senior Research Scientist
Cooperative Institute for Research in Environmental Sciences (CIRES)
University of Colorado Boulder/NOAA Chemical Sciences Laboratory
February 19, 2021
I commend the authors for undertaking this endeavor, which will serve as an excellent historical reference for our field of research. I will limit my comments and suggestions to Section 2.16
Section 2.16 provides a short review of key papers on Chemical Transport. It starts out well with a discussion of STE and recognition of Danielsen 1968 and Holton et al. 1995, but it needs a better connection to the STE review article by Stohl et al. 2003, which appears much further down (on Line 887), after the concept of long range transport is introduced. This paper should appear in the paragraph on STE.
Before recognizing the important study by Jacob et al. 1999 (which is based on a model rather than observations) some key observational studies should be recognized, for demonstrating that long-range and intercontinental transport clearly occurs.
These studies are as follows:
Merrill et al. (1985) (cited 124 times) used isentropic back trajectories to link transport from Asia and North/Central America to the Marshall Islands
Moody et al., 1995 (cited 114 times) also used isentropic back trajectories to link transport from North America to Bermuda.
Stohl and Trickl, 1999 (cited 214 times) were the first to show that a warm conveyor belt can transport pollution from one continent to another, in this case, ozone from the boundary layer of North America to the free troposphere above Europe.
Forster et al., 2001 (cited 225 times) used kinematic back trajectories (FLEXTRA) to show that smoke from biomass burning in Canada could reach the boundary layer of Europe, and they showed that due to the thermal structure of the atmosphere, this transport has to occur at low levels behind cold fronts rather than in warm conveyor belts.
In addition to being great, groundbreaking studies, the papers by Moody et al. 1995 and Forster et al. 2001 are also notable because they were led by women at a time when the field was still dominated by men.
Regarding the discussion of trajectory methods, the earlier and more simplistic isentropic trajectory method (Merrill et al., 1985) should be mentioned before HYSPLIT.
Forster, C., Wandinger, U., Wotawa, G., James, P., Mattis, I., Althausen, D., Simmonds, P., O'Doherty, S., Jennings, S.G., Kleefeld, C. and Schneider, J., 2001. Transport of boreal forest fire emissions from Canada to Europe. Journal of Geophysical Research: Atmospheres, 106(D19), pp.22887-22906.
Merrill, J. T., Bleck, R., and Avila, L. (1985), Modeling atmospheric transport to the Marshall Islands, J. Geophys. Res., 90( D7), 12927– 12936, doi:10.1029/JD090iD07p12927.
Moody, J.L., Oltmans, S.J., Levy, H. and Merrill, J.T., 1995. Transport climatology of tropospheric ozone: Bermuda, 1988–1991. Journal of Geophysical Research: Atmospheres, 100(D4), pp.7179-7194.
Stohl, A. and Trickl, T., 1999. A textbook example of long‐range transport: Simultaneous observation of ozone maxima of stratospheric and North American origin in the free troposphere over Europe. Journal of Geophysical Research: Atmospheres, 104(D23), pp.30445-30462.-
AC11: 'Reply on CC12', Paul Monks, 28 Jun 2021
Thank-you for the comments. As suggested the Stohl STE review has been moved to the section that discusses STE. It was clear that the observational perspective in respect of long-range transport was missing, therefore the suggested references have been added to section 2.16. Small update on methodologies for trajectories added.
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AC11: 'Reply on CC12', Paul Monks, 28 Jun 2021
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CC13: 'Comment on acp-2020-1266', A.R.,. Ravishankara, 20 Feb 2021
We thank all colleagues who has posted various suggestions. We will attempt to incorporate all the comments to the best of our abilities.
We invited any other comments from colleagues.
- AC13: 'Reply on CC13', Paul Monks, 28 Jun 2021
- AC14: 'Reply on CC13', Paul Monks, 28 Jun 2021
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CC14: 'Comment on acp-2020-1266', Gary Bishop, 22 Mar 2021
I will add my support for some additional references to the chemiluminescence detection of NO/NO2. While Leighton's photostationary state hypothesis was fully established as you point out by the early 90's that establishment involved lots of measurements using the chemiluminescence detector. During the 70's and 80's the device was likely responsible for most of the NO/NO2 measurements used for determining the jNO2 which was crtical for model chemistry. I am not as widely read for this topic during this time period but papers by my former boss, Don Stedman, and others that I am aware of for a starting point are:
D. H. Stedman, J. O. Jackson, "The photostationary state in photochemical smog" Intern. J. Chem. Kinetics Symp. I: 493
(1975).D. Kley, M. McFarland, "Chemiluminescence detector for NO and NO2," Atmos. Technol. 12:63 (1980)
R. E. Shetter, D. H. Stedman, and D. H. West, "The NO/NO2/O3 Photostationary State in Claremont, California," J. Air Poll. Cont. Assoc. 33:3, 212-214, 1983.
As a side note for the importance of the chemiluminescence detector for NO2. Don flew one on a commercial flight between Denver and Boston and included the data in the final report for the National Research Council entitled "The Airliner Cabin Environment Air Quality and Safety Committee on Airliner Cabin Air Quality" in 1986 which recommended a ban of smoking on commercial aircraft. That data highigted the absurdity that limiting the number of smoking rows to a few in the back of the plan spared others from the exposure. This report led to the eventual ban of smoking on US flights and laid the groundwork for all of the current limits on smoking because of the potentail negative health effects.
The following comments are totally self-serving and I point this out so that the authors can choose to totally ignore them solely on that basis if they so choose. The paragraph in the emission section on vehicle emissions includes 4 references. The works of Calvert et al., Lawson and Singer and Harley use data either in part, Calvert et. al. and Lawson, or entirely (Singer and Harley) to form a basis of their works that was collected using a remote sensing device invented by Don Stedman. The work described by Chaney was important in the development of the device Don invented as it gave Don the initial idea (he was a colleague of Chaney and involved in his work) but the method described by Chaney was a simple time series of a single species, carbon monoxide, captured alongside a road that implied that individual vehicle plumes could be capture if one had a fast enough detector. Chaney's work provides no way for those CO measurements to be turned into fuel specific emissions that could be used for vehicle emission comparisons or inventory calculations that Calvert, Lawson and Singer an Harley rely upon in their works. It was not until Don demonstrated the high speed measurement of pollution ratio's to carbon dioxide for vehicle exhaust emissions that made this possible.
Final comment on emissions the papers by Calvert et al., Lawson and Singer and Harley do not really "verify" the California Smog Control Program. If anything these papers call into question how well these control programs actually work and strongely suggest that it is significantly less that the State believes. At the time of writing of these papers California was in denial that a small portion of the fleet was responsible for a large proportion of the total emissions. In the state's mind high emitters did not exist because all of the control programs had eliminated them. Years of measurements subsequently have proven this idea wrong.
Thanks for the effort taken so far in providing a thourougly entertainting and educational look back at all the work that has combined to get us to where we are today in our understanding of Atmospheric Chemistry.
Gary Bishop
University of Denver-
AC17: 'Reply on CC14', Paul Monks, 28 Jun 2021
The gap with respect to PSS and the chemiluminescence measurement of NO/NO2 is acknowledged. The Kley and McFarland (1980) reference has been added. Following the comments on Stedman's work on the measurement and quantification of exhaust emissions suitable reference has been added. The authors are grateful for the thought comments.
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AC17: 'Reply on CC14', Paul Monks, 28 Jun 2021
Status: closed
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CC1: 'Comment on acp-2020-1266', Joel Savarino, 05 Jan 2021
Dear authors
thank you for gathering this corpus of founding articles to understand the construction, evolution and fundamental discoveries of this discipline that is the chemistry of the atmosphere. This article will remain a reference and an entry point for the new generation of researchers, as well as for the older generation to understand its field and progress.
As indicated at the end of the article, I would like to provide additional information. It seems to me that Lovelock's article (1) and his discovery of DMS (thanks to his invention of the ECD detector (2) which also allowed the first measurements of CFCs) as the reduced sulfur compound emitted by themarine biota(and not H2S as thought previously) would have its place in this article. This article also advances the idea that the MSA resulting from the oxidation of DMS is a probable source of aerosols. It is on the basis of this article that the CLAW hypothesis was born. This article deserves to be mentioned.
In the same vein, I think Patterson's paper on the increase of lead in the air (3) (actually in snow) as well as its decrease since the elimination of lead in gasoline (4) would be worth mentioning. With the elimination of CFCs, this is the other major victory of atmospheric chemistry research over environmental policy.
With regards
1- Lovelock, J. E., Maggs, R. J., and Rasmussen, R. A.: Atmospheric Dimethyl Sulphide and the Natural Sulphur Cycle, Nature, 237, 452-453, 10.1038/237452a0, 1972.2- Lovelock, J. E., SR Lipsky,Electron Affinity Spectroscopy-A New Method for the Identification of Functional Groups in Chemical Compounds Separated by Gas Chromatography -Journal of the American Chemical, 82, 431, 1960.
3-Murozumi, M., Chow, T. J., and Patterson, C. (2003): Chemical concentrations of pollutant lead aerosols, terrestrial dusts and sea salts in Greenland and Antarctic snow strata, Geochim. Cosmochim. Acta, 33, 1247-1294, https://doi.org/10.1016/0016-7037(69)90045-3, 1969.
4-Boutron, C. F., Görlach, U., Candelone, J.-P., Bolshov, M. A., and Delmas, R. J.: Decrease in anthropogenic lead, cadmium and zinc in Greenland snows since the late 1960s, Nature, 353, 153-156, 10.1038/353153a0, 1991.
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AC10: 'Reply on CC1', Paul Monks, 28 Jun 2021
Thank-you for the comments. With respect to the Lovelock ECD work, the reference and description has been added to the VOC section. The extra information on the MSA/DMA Lovelock work has been added to the description of CLAW hypothesis. Further, a small section on lead including the suggested works have been added to the foundations section.
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AC10: 'Reply on CC1', Paul Monks, 28 Jun 2021
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CC2: 'Comment on acp-2020-1266', Pawan Gupta, 05 Jan 2021
Page 35, Section 2.17 - "A step-change in this area was made with the paper “Estimating 929 ground-level PM2.5 using aerosol optical depth determined from satellite remote sensing” by van Donkelaar et al. (2006) which was the first description of the derivation of surface PM2.5 from satellite AOD, and which has been extensively used to estimate the global impact of particulate matter (both PM2.5 and PM10) on health"
It appears that the above assessment is not correct.
The first paper showing quantitative PM2.5 estimation using satellite AOD was published in 2003 as 'Wang, J., and S. A. Christopher, Intercomparison between satellite-derived aerosol optical thickness and PM2.5 mass: Implications for air quality studies, Geophys. Res. Lett., 30(21), 2095, doi:10.1029/2003GL018174, 2003'
introduced a simple statistical method to estimate PM2.5 using satellite data, later on, the following paper by Liu et al., (2004)
"Liu, Y., Park, R. J., Jacob, D. J., Li, Q., Kilaru, V., and Sarnat, J. A. (2004), Mapping annual mean ground‐level PM2.5 concentrations using Multiangle Imaging Spectroradiometer aerosol optical thickness over the contiguous United States, J. Geophys. Res., 109, D22206, doi:."
first introduced the model scaling approach, which was later adopted by van Donkelaar et al. (2006) and resulted in global estimates of PM2.5 at annual mean levels.
Over the last two decades, there have been several hundreds of papers published in assessing the satellite-derived AODs to estimate surface particulate matter air quality.
- AC8: 'Reply on CC2', Paul Monks, 28 Jun 2021
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CC3: 'Comment on acp-2020-1266', Viney Aneja, 05 Jan 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-CC3-supplement.pdf
- AC3: 'Reply on CC3', Paul Monks, 28 Jun 2021
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CC4: 'Comment on acp-2020-1266', Sandro Fuzzi, 07 Jan 2021
I want to congratulate the authors for putting together this interesting overview based on a series of suggestions from the science community.
In the spirit of collaboration that the authors ask for, I have a few comments.
- AC16: 'Reply on CC4', Paul Monks, 28 Jun 2021
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CC5: 'Comment on acp-2020-1266', Sandro Fuzzi, 08 Jan 2021
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AC15: 'Reply on CC5', Paul Monks, 28 Jun 2021
With respect to the comparison in Table 1 (revised version, Table 2 in submitted version), we felt it useful to highlight the differences and also shortcomings of a solely metric approach (as highlighted in the text). The difference remarked on is the very essence of the problem.
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AC15: 'Reply on CC5', Paul Monks, 28 Jun 2021
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CC6: 'Comment on acp-2020-1266', Sandro Fuzzi, 08 Jan 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-CC6-supplement.pdf
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AC7: 'Reply on CC6', Paul Monks, 28 Jun 2021
We did consider this idea "Appendix 1 shows very interesting results on journalsand regions of the references reported in the paper. I would suggest to include an Appendix 2 reported similar statistics concerning the contributions received by the authors from the call through the IGAC community." but for two reasons decided not to do it. The first was to avoid the top 10 lists mentality and the second was with just over 50 contributors the statistics where not robust.
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AC7: 'Reply on CC6', Paul Monks, 28 Jun 2021
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CC7: 'Comment on acp-2020-1266', Nick Hewitt, 14 Jan 2021
Thanks for this excellent overview of atmopheric chemistry research. It made really interesting reading.
I have a suggestion to make about section 2.13 on biogenic VOCs. Please see the linked document.
- AC4: 'Reply on CC7', Paul Monks, 28 Jun 2021
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CC8: 'Comment on acp-2020-1266', David Griffith, 15 Jan 2021
Dear Paul, Ravi et al.,
Thank you for the considerable effort in putting this history together – to one active in the field since the late 1970s (when the curve in Fig 1 kicks off), it is an enjoyable read, and a trip down memory lane.
Inevitably, having solicited them, you will get lots of suggestions for things that you have left out or rated less important than judged by others. Already there are several… So I will add mine, for your consideration. Two areas in my view deserve their own explicit subsection of section 2. Some aspects are already mentioned in passing in several places, but my judgement would be that they deserved their own explicit subsection.
- Measurement techniques. We might divide up the whole topic into two sub topics – the chemistry itself, and the methods used to probe it. Many advances in our understanding of atmospheric chemistry have come from stepwise advances in measurement (and modelling) capabilities. There are already explicit sections for kinetics, models, meteorology and transport and satellite measurements, but nothing explicitly for chemical measurement techniques. The success of the high impact journal AMT speaks for the importance. Examples of discoveries that might be included in this area might be (but are not limited to):
- The ECD detector (Lovelock), which enabled the detection of halocarbons
- PTR-MS – already mentioned in 2.12 in the VOC context
- OH measurements – LIF etc.
- The chemiluminescence technique for NO and NOx
- Dobson method for O3 (admittedly stratospheric)
- Satellite retrievals – satellite global mapping of composition has been a real revolution.
- Greenhouse and climate-relevant gases (and aerosols). Given the current state and importance of climate change science and policy, a separate section on greenhouse and other climate-relevant species seems to me to be very desirable. There are some mentions throughout, eg to Keeling and to long term monitoring networks like ALE/AGAGE. GAW, NOAA, ICOS, but it would be valuable to bring them together into their own section. Also the techniques that enable reliable and accurate long term records to be maintained – NDIR, optical in situ and remote sensing techniques, isotopic methods, and satellite measurements (again).
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AC12: 'Reply on CC8', Paul Monks, 28 Jun 2021
Thank you for the comments, in respect of
1. Measurement techniques
1. The ECD detector (Lovelock), which enabled the detection of halocarbons Reference to the Lovelock work on ECD added to VOC section 2. PTR-MS – already mentioned in 2.12 in the VOC context PTR-MS discussed in section 2.12 3. OH measurements – LIF etc. References and discussion added, on instrumentation and OH measurement 4. The chemiluminescence technique for NO and NOx Reference to original work from Kley and McFadden added 5. Dobson method for O3 (admittedly stratospheric) Added full historical context of stratospheric ozone 6. Satellite retrievals – satellite global mapping of composition has been a real revolution. The section on satellite measurements reflects this. 2. Greenhouse and climate-relevant gases (and aerosols) - The long-term measurements of GHG and other climate relevant gases was missing. A small section highlighting some of the main measurement networks has been added, plus additional information on the value of long-term measurements.
- Measurement techniques. We might divide up the whole topic into two sub topics – the chemistry itself, and the methods used to probe it. Many advances in our understanding of atmospheric chemistry have come from stepwise advances in measurement (and modelling) capabilities. There are already explicit sections for kinetics, models, meteorology and transport and satellite measurements, but nothing explicitly for chemical measurement techniques. The success of the high impact journal AMT speaks for the importance. Examples of discoveries that might be included in this area might be (but are not limited to):
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RC1: 'Comment on acp-2020-1266', Anonymous Referee #1, 18 Jan 2021
This is a wonderful paper that will provide many future generations of atmospheric scientists some perspective on how the field developed and its current status. The limitations and approach taken are clearly stated and their emphasis on integrating all aspects of the field, ambient measurements, lab studies and modeling, is terrific.
This reviewer has just a few suggestions and minor typo's etc.
- Line 34: Suggest adding at least one other review from the health community re: human health impacts, e.g. by Landrigan et al in Lancet, 2018. The introduction says it is only treating papers 2010 and earlier but cites a 2015 Lelieveld paper for health effects so I assume later papers than 2010 are being cited for background?
- Throughout, the word "aerosols" is used to denote "particles". Historically, the engineers who developed much of this area and the instrumentation have defined aerosols as particles and the gas in which they are suspended (e.g. see Hinds book). This would be a good place to exhibit consistency and use "aerosol particles" throughout, or just "particles" if that is what they mean.
- Line 360: As the authors indicate in the introduction, the fundamental work on which significant advances are made often ends up not being cited as the field develops. The laser ionization MS technique I think originated with Sinha, Rev. Sci. Instrum. (1984), followed by papers coauthored with Friedlander. It might be appropriate to include one of these references along with Prather and Murphy.
- Line 367: I would add for clarity at the end of the sentence on this line "that assumed low viscosity, liquid-like particles where exchange with the gas phase is fast".
- Line 445: They state that the "distinction between heterogenous and multiphase chemistry is not always clear". This would be a good place to define these terms.
- Lines 453-469: These two paragraphs mix multiphase and heterogenous chemistry in a somewhat random order. I think they are using "heterogeneous" to mean reactions at surfaces and "multiphase" to mean reactions involving the uptake of gases into (and reaction in) the liquid phase. It would be good to define the terms first and then separate out the examples they give into the two bins.
- Line 455-459: This cites the work of Akimoto et al on the photoenhancement of HONO formation but it seems some discussion of the dark formation of HONO should come first. The Pitts et al, Int. J. Chem. Kin. (1984) might be the first discussion of this in chambers. Finlayson-Pitts et al, PCCP (2003) is a review of the area to that point.
- Lines 571-573: It reads as if Sillman (1999) was the first to put together ozone isopleths but this goes back into the 1950's or 60's, probably Haagen-Smit and Fox (1954). It would be good to cite the origins here as it is so important to our understanding even today.
- Lines 685-692: Shroeder and Urone (EST, 1974) were probably the first to suggest sea salt reactions as a photochemical source of chlorine atoms. It could be cited here and on line 704. A review by Cicerone in Rev. Geophys. Space Phys. (1981) would be a good review too.
- Line 846: It seems odd to state that emission inventories were pioneered in the 1990's. Surely they were being developed long before that, at least in California?
- Lines 925-927: Satellites have been really useful for tracking dust events but it seems that either here or in another section a reference to the seminal studies on dust transport of Prospero et al in the 1970's should be included.
- Line 988: "by now phased out the ozone-depleting gases". I think this is overly optimistic to say this, given recent measurements showing there seem to be emissions from Asia that were not expected. Maybe "are now phasing out ozone-depleting gases"...
- Table 1 seems quite Euro-centric, for example not including some of the big smog events in the U.S. and the passage of the Clean Air Act etc.
- Table 2 is in two parts. It was not clear to this reviewer how they differ from each other in what they are supposed to illustrate.
- Table 3 seems out of context. It is very detailed on NOx but similar detail is not given for other species. I suggest omitting this.
- Appendix 1 data go to 2020. Since the focus of the article is 2010 and prior years, some comment in the captions might be appropriate.
Minor typos, grammar etc:
- Line 34: impacts.
- Line 35: "latterly links to their climate" is very awkward. Maybe replace "latterly links to their climate" with "and climate"
3.Line 178: "pollutions"
- Line 626: "any" should be "many"?
- Line 824: "..most cited paper"
- Line 885: Should "The study" be omitted so the sentence starts: "Moody et al (1998) ..."
- Line 900: Spelling error "emmited"
- The formatting of the references (no space between etc) makes them very hard to read but I suppose that will get straightened out in the final document.
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AC2: 'Reply on RC1', Paul Monks, 28 Jun 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-AC2-supplement.pdf
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CC9: 'Comment on Emission and Deposition', Thomas Karl, 21 Jan 2021
This is an excellent and broad perspective on tropospheric chemistry. As such it will certainly become a valuable reference and resource. As already pointed out by Nick Hewitt, it was actually Sanadze who first reported substantial isoprene emissions from plants in Russia (1957). Rasmussen independently found similar results in the US. I highly recommend the review article by Sharkey and Monson on 60 years of isoprene research. (Isoprene research – 60 years later, the biology is still enigmatic, doi: 10.1111/pce.12930, 2017). Further it is mentioned that "recent interest in deposition reemerged", but that physio-chemical parameters are lacking. Physio – chemical parameters for most gases (e.g. HLC, vapor pressure, reactivity etc.) are very well established and an important reason why the ‘Wesely scheme’ works quite well for classic air pollutants over many surface types. I would argue that the complication stems more from a range of oxygenated VOC that can exhibit bi-directional exchange above vegetation (e.g. doi: 10.1126/science.1192534, doi: 10.1126/science.1235053). Moreover it was recently demonstrated that plants can also "reprocess" OVOCs, produced during atmospheric oxidation, through enzymatic reactions (doi: 10.1038/s43247-020-00041-2 ). The concept of bi-directional exchange is not included in the theoretical framework of emission and deposition models as there is little need for most gases. Yet, it is somewhat overlooked when discussing the fate of reactive organic carbon as many oxygenated volatile species can reside in this no-man’s land.
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CC11: 'Reply on CC9', Paul O. Wennberg, 19 Feb 2021
Indeed, deposition (and emission) of oxygenated VOCs is an important new frontier.
Nguyen et al., 2015 ( https://www.pnas.org/content/112/5/E392 ) and Wolfe et al., 2015 ( https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL065839 ) evaluated such fluxes against the Wesley scheme and illustrated some of the shortfalls.
- AC6: 'Reply on CC11', Paul Monks, 28 Jun 2021
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AC9: 'Reply on CC9', Paul Monks, 28 Jun 2021
Thank-you for the insightful comments. The correction made as to origin of isoprene and excellent review article from Sharkey and Monson has been added. With respect to the second point around bi-directional fluxes, a senetence and reference has been added to capture this point.
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CC11: 'Reply on CC9', Paul O. Wennberg, 19 Feb 2021
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CC10: 'HONO_Comment on acp-2020-1266', Yasin Elshorbany, 25 Jan 2021
I commend the authors for leading this nice effort and inspired by the call for contributions, I have a few suggestions. I am missing a discussion on nitrous acid (HONO) which has emerged as a major source of OH radical during the last 15 years.
Here is a relevant draft summary:
HONO photolysis is a major OH source, especially during the early morning, which was first identified by Perner and Platt (1979):
HONO + hν (λ < 400nm) → OH + NO
During the daytime, photolysis of HONO has been shown to be the most important OH initiation source under urban high NOx conditions (e.g., Elshorbany et al., 2009a, 2009b) and was found to have a significant impact on ozone photochemical formation (Elshorbany et al., 2010). HONO was also demonstrated to have large global impact on gas phase (Elshorbany et al., 2012) and aerosol formation (Elshorbany et al., 2014).
HONO is now recognized as an important species that is being measured routinely during field measurements. Attempts are currently underway to detect it from space, which is being challenged by its low near-surface concentrations but was recently detected in biomass burning emissions.
HONO research is driven by unexpected high daytime values of HONO (e.g. Neftel et al., 1996, Zhou et al., 2002; Kleffmann et al., 2002; Acker et al., 2006a, 2006b, Elshorbany et al, 2009). Several photochemical HONO sources have been proposed (Kleffmann, 2007), some of which have been identified in the laboratory (e.g., Zhou et al., 2003; George et al., 2005; Stemmler et al., 2006, 2007; Bejan et al., 2006; Li et al., 2008, Gustafsson et al., 2006; Ndour et al., 2008). HONO sources in the atmosphere are not yet well understood. While the dark heterogeneous conversion of NO2 on humid surfaces (Finlayson-Pitts et al., 2003) is commonly accepted as the dominant HONO sources during night (Alicke et al., 2002), the exact mechanism is still unclear:
2 NO2 + H2O → HONO + HNO3
In addition, recent studies showed that the heterogeneous reaction of NO2 with adsorbed hydrocarbons are also important under atmospheric conditions (Ammann, et al., 2005).
NO2 + Organics(red) → HONO + Organics(oxi.)
For HONO daytime sources, five photochemical mechanisms were recently identified. Three of them dominate under high NOx urban conditions, namely heterogeneous conversion of gaseous NO2 on photosensitized solid surface organic compounds (George et al., 2005; Stemmler et al., 2006), photocatalytic conversion of NO2 on TiO2 (Gustafsson et al., 2006; Ndour et al., 2008) and the photolysis of the gaseous nitroaromatic compounds (Bejan et al., 2006) and should correlate well with j(NO2). Under low NOx rural conditions, the photolysis of nitric acid (Zhou et al., 2003) adsorbed on solid surfaces (including vegetations) may dominate and would better correlate to j(O1D), caused by the much lower wavelength range of the nitric acid photolysis.
- AC5: 'Reply on CC10', Paul Monks, 28 Jun 2021
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RC2: 'Comment on acp-2020-1266', Anonymous Referee #2, 03 Feb 2021
Review of the paper by Monks et al entitled “Opinion: Papers that shaped Tropospheric Chemistry”.
This wonderful paper represents a very important contribution because it shows the evolution of an important research field until year 2010. It will provide to the new generations of students and scientists an excellent historical introduction that will allow them to realize how the concepts have evolved and how science progresses. It is particularly interesting to understand that progress in atmospheric chemistry resulted from the complementarity between laboratory experiments, field measurements, data analysis and modeling.
I like the paper very much. I will highlight its strengths but I will also make some suggestions to make the paper somewhat more inclusive. I find the paper a bit unbalanced towards process studies and laboratory work (which should be highlighted as they are) at the expense of field work and modeling.
Strength of the Paper
The paper covers a lot of material and reports a lot of important results that shaped the field of atmospheric chemistry. A lot of bibliographical material is provided. Several graphs and tables are very interesting including, for example, the documents by sources and year and by country. The two tables with the top 10 cited papers are useful.
The grouping of 19 topics presented in Section 1.2 is excellent.
The discussion about how the papers were selected and the limitations to this approach is very good. It shows that the methodology does not provide an absolute standard and that work not included in this list can also be excellent.
The paper is well written and easy to read. I am sure that people starting their career will like to read the document.
Suggestions.
As I said above, I find the paperto be a bit unbalanced towards fundamental processes at the expense of more global and regional investigations. This could be easily addressed by adding some references to a few important observational and modeling accomplishments. Sometimes, big advances related, for example, to filed campaigns are not presented as a single paper, but are dispersed in several papers, and so none of them has a highest citation rate. For example, a major accomplishment before 2010 has been the organization of several airborne campaigns. Not only the ER-2 measurements of the ClO/O3 reactions have been key for the ozone hole question, but also the numerous airborne field campaigns in the 1980’s and 1990’s (many NASA field campaigns) that have provided insight on global tropospheric chemistry, and in particular on questions related to the oxidation capacity of the atmosphere.
A lot has been learned from field campaigns (such as PEM, Trace P, ACE, and several others) and so perhaps, the authors could mention large projects that have provided fundamental understanding of the functioning of the atmosphere at the global and regional scales. Other topics that illustrate major advances:
Field campaigns to assess NOx produced by lightning and the importance of thunderstorms
Production of methane by rice paddies, particularly in Asia
Monitoring of methane and carbon monoxide by international networks
Systematic observations of ozone and CO from commercial aircraft
Perhaps a bit more should be said about space observations. Much progress has been done before year 2010. The measurement of CO from the Space Shuttle gave a first global view of the distribution of this species and highlighted the role of biomass burning, particularly in the tropics. Beside GOME, and SCIAMACHY, one should perhaps refer to other important satellites and instruments such as OMI, MOPITT, MODIS, TES, etc. since they provided again a global view that was very useful to understand global budgets and the role of transport.
Finally, the Section on modeling is a bit weak. Models have been key for the interpretating observations, analyzing the role of chemical processes and projecting future changes in the atmospheric composition. The first relatively detailed 3-D model of the troposphere (although a bit intermediate) were developed in Mainz (MONGUNTIA), in Brussels (IMAGES) and at Livermore (GRANTOUR). They were followed by major efforts to develop really comprehensive chemical transport models (GeosChem at Harvard, MOZART at NCAR, Uni. Of Oslo model, and MESSY in Mainz, CHASER in Japan, etc.
For stratospheric work, which is also mentioned in the paper, 2-D models such as the model of Garcia and Solomon have been a key tool to implement the fundamental concepts of the stratospheric residual circulation (and related meridional transport) resulting from planetary wave breaking presented by Holton and McIntyre, and to assess how the residual circulation could explain the meridional transport of ozone and other tracers in the middle atmosphere. Several 3-D stratospheric models were also developed for the stratosphere. One of the first ones was developed at MIT by Cunnold, Aleya and Prinn and at GFDL by Mahlman. Some more advanced models include WACCM developed at NCAR
Nothing is said about the first attempts to develop inverse modeling techniques and chemical data assimilation methodologies, which were initiated in the late 1990s.
I do not want to provide a “list of what is missing” since the goal of the paper is to highlight bthe most cited papers, but I am making some general points that perhaps would be welcome, and I am not asking to the authors to necessarily including all of them in the text. These are just constructive suggestions.
Some minor remarks on the text
Around line 109: How many responses were provided in response your solicitation of the scientific community?
Line 320; Can you add a reference and perhaps an estimate of the uncertainty about the -1.1 Wm-2 ?
Figure 4 looks dark to me and low quality (it may be my printer).
Lines 364 to 367: Difficult to understand if you are not specialized (amorphous solid state). Beside the fact that it challenged the traditional views, what are the consequences of this discovery?
Line 539: Second or third? I thought that methane was second (and close to ozone).
Figure 10: the figure does not read well. Complicated to understand with such a short caption. Also, on the y-scale, it seems strange to express an integrated flux in ppb. I guess that it is integrated over time, but for how long.
Line 742: I am not sure that research is trying to count the numbers of VOCs present in the atmosphere.
Line 949: It is appropriate to cite Hampson, but a reference to his report should be added.
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AC1: 'Reply on RC2', Paul Monks, 28 Jun 2021
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2020-1266/acp-2020-1266-AC1-supplement.pdf
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AC1: 'Reply on RC2', Paul Monks, 28 Jun 2021
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CC12: 'Comment on acp-2020-1266', Owen Cooper, 20 Feb 2021
Comment by:
Owen R. Cooper
Senior Research Scientist
Cooperative Institute for Research in Environmental Sciences (CIRES)
University of Colorado Boulder/NOAA Chemical Sciences Laboratory
February 19, 2021
I commend the authors for undertaking this endeavor, which will serve as an excellent historical reference for our field of research. I will limit my comments and suggestions to Section 2.16
Section 2.16 provides a short review of key papers on Chemical Transport. It starts out well with a discussion of STE and recognition of Danielsen 1968 and Holton et al. 1995, but it needs a better connection to the STE review article by Stohl et al. 2003, which appears much further down (on Line 887), after the concept of long range transport is introduced. This paper should appear in the paragraph on STE.
Before recognizing the important study by Jacob et al. 1999 (which is based on a model rather than observations) some key observational studies should be recognized, for demonstrating that long-range and intercontinental transport clearly occurs.
These studies are as follows:
Merrill et al. (1985) (cited 124 times) used isentropic back trajectories to link transport from Asia and North/Central America to the Marshall Islands
Moody et al., 1995 (cited 114 times) also used isentropic back trajectories to link transport from North America to Bermuda.
Stohl and Trickl, 1999 (cited 214 times) were the first to show that a warm conveyor belt can transport pollution from one continent to another, in this case, ozone from the boundary layer of North America to the free troposphere above Europe.
Forster et al., 2001 (cited 225 times) used kinematic back trajectories (FLEXTRA) to show that smoke from biomass burning in Canada could reach the boundary layer of Europe, and they showed that due to the thermal structure of the atmosphere, this transport has to occur at low levels behind cold fronts rather than in warm conveyor belts.
In addition to being great, groundbreaking studies, the papers by Moody et al. 1995 and Forster et al. 2001 are also notable because they were led by women at a time when the field was still dominated by men.
Regarding the discussion of trajectory methods, the earlier and more simplistic isentropic trajectory method (Merrill et al., 1985) should be mentioned before HYSPLIT.
Forster, C., Wandinger, U., Wotawa, G., James, P., Mattis, I., Althausen, D., Simmonds, P., O'Doherty, S., Jennings, S.G., Kleefeld, C. and Schneider, J., 2001. Transport of boreal forest fire emissions from Canada to Europe. Journal of Geophysical Research: Atmospheres, 106(D19), pp.22887-22906.
Merrill, J. T., Bleck, R., and Avila, L. (1985), Modeling atmospheric transport to the Marshall Islands, J. Geophys. Res., 90( D7), 12927– 12936, doi:10.1029/JD090iD07p12927.
Moody, J.L., Oltmans, S.J., Levy, H. and Merrill, J.T., 1995. Transport climatology of tropospheric ozone: Bermuda, 1988–1991. Journal of Geophysical Research: Atmospheres, 100(D4), pp.7179-7194.
Stohl, A. and Trickl, T., 1999. A textbook example of long‐range transport: Simultaneous observation of ozone maxima of stratospheric and North American origin in the free troposphere over Europe. Journal of Geophysical Research: Atmospheres, 104(D23), pp.30445-30462.-
AC11: 'Reply on CC12', Paul Monks, 28 Jun 2021
Thank-you for the comments. As suggested the Stohl STE review has been moved to the section that discusses STE. It was clear that the observational perspective in respect of long-range transport was missing, therefore the suggested references have been added to section 2.16. Small update on methodologies for trajectories added.
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AC11: 'Reply on CC12', Paul Monks, 28 Jun 2021
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CC13: 'Comment on acp-2020-1266', A.R.,. Ravishankara, 20 Feb 2021
We thank all colleagues who has posted various suggestions. We will attempt to incorporate all the comments to the best of our abilities.
We invited any other comments from colleagues.
- AC13: 'Reply on CC13', Paul Monks, 28 Jun 2021
- AC14: 'Reply on CC13', Paul Monks, 28 Jun 2021
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CC14: 'Comment on acp-2020-1266', Gary Bishop, 22 Mar 2021
I will add my support for some additional references to the chemiluminescence detection of NO/NO2. While Leighton's photostationary state hypothesis was fully established as you point out by the early 90's that establishment involved lots of measurements using the chemiluminescence detector. During the 70's and 80's the device was likely responsible for most of the NO/NO2 measurements used for determining the jNO2 which was crtical for model chemistry. I am not as widely read for this topic during this time period but papers by my former boss, Don Stedman, and others that I am aware of for a starting point are:
D. H. Stedman, J. O. Jackson, "The photostationary state in photochemical smog" Intern. J. Chem. Kinetics Symp. I: 493
(1975).D. Kley, M. McFarland, "Chemiluminescence detector for NO and NO2," Atmos. Technol. 12:63 (1980)
R. E. Shetter, D. H. Stedman, and D. H. West, "The NO/NO2/O3 Photostationary State in Claremont, California," J. Air Poll. Cont. Assoc. 33:3, 212-214, 1983.
As a side note for the importance of the chemiluminescence detector for NO2. Don flew one on a commercial flight between Denver and Boston and included the data in the final report for the National Research Council entitled "The Airliner Cabin Environment Air Quality and Safety Committee on Airliner Cabin Air Quality" in 1986 which recommended a ban of smoking on commercial aircraft. That data highigted the absurdity that limiting the number of smoking rows to a few in the back of the plan spared others from the exposure. This report led to the eventual ban of smoking on US flights and laid the groundwork for all of the current limits on smoking because of the potentail negative health effects.
The following comments are totally self-serving and I point this out so that the authors can choose to totally ignore them solely on that basis if they so choose. The paragraph in the emission section on vehicle emissions includes 4 references. The works of Calvert et al., Lawson and Singer and Harley use data either in part, Calvert et. al. and Lawson, or entirely (Singer and Harley) to form a basis of their works that was collected using a remote sensing device invented by Don Stedman. The work described by Chaney was important in the development of the device Don invented as it gave Don the initial idea (he was a colleague of Chaney and involved in his work) but the method described by Chaney was a simple time series of a single species, carbon monoxide, captured alongside a road that implied that individual vehicle plumes could be capture if one had a fast enough detector. Chaney's work provides no way for those CO measurements to be turned into fuel specific emissions that could be used for vehicle emission comparisons or inventory calculations that Calvert, Lawson and Singer an Harley rely upon in their works. It was not until Don demonstrated the high speed measurement of pollution ratio's to carbon dioxide for vehicle exhaust emissions that made this possible.
Final comment on emissions the papers by Calvert et al., Lawson and Singer and Harley do not really "verify" the California Smog Control Program. If anything these papers call into question how well these control programs actually work and strongely suggest that it is significantly less that the State believes. At the time of writing of these papers California was in denial that a small portion of the fleet was responsible for a large proportion of the total emissions. In the state's mind high emitters did not exist because all of the control programs had eliminated them. Years of measurements subsequently have proven this idea wrong.
Thanks for the effort taken so far in providing a thourougly entertainting and educational look back at all the work that has combined to get us to where we are today in our understanding of Atmospheric Chemistry.
Gary Bishop
University of Denver-
AC17: 'Reply on CC14', Paul Monks, 28 Jun 2021
The gap with respect to PSS and the chemiluminescence measurement of NO/NO2 is acknowledged. The Kley and McFarland (1980) reference has been added. Following the comments on Stedman's work on the measurement and quantification of exhaust emissions suitable reference has been added. The authors are grateful for the thought comments.
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AC17: 'Reply on CC14', Paul Monks, 28 Jun 2021
Paul S. Monks et al.
Paul S. Monks et al.
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