The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4)
<p><span id="page2540"/>The representation of volatile organic compound (VOC) deposition and oxidation mechanisms in the context of secondary organic aerosol (SOA) formation are developed in the United Kingdom Chemistry and Aerosol (UKCA) chemistry–climate model. Impacts of the...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2019-06-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://www.geosci-model-dev.net/12/2539/2019/gmd-12-2539-2019.pdf |
| _version_ | 1818268842106814464 |
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| author | J. M. Kelly J. M. Kelly R. M. Doherty F. M. O'Connor G. W. Mann H. Coe D. Liu |
| author_facet | J. M. Kelly J. M. Kelly R. M. Doherty F. M. O'Connor G. W. Mann H. Coe D. Liu |
| author_sort | J. M. Kelly |
| collection | DOAJ |
| description | <p><span id="page2540"/>The representation of volatile organic compound (VOC) deposition and
oxidation mechanisms in the context of secondary organic aerosol (SOA)
formation are developed in the United Kingdom Chemistry and Aerosol (UKCA)
chemistry–climate model. Impacts of these developments on both the global SOA
budget and model agreement with observations are quantified. Firstly, global
model simulations were performed with varying VOC dry deposition and wet
deposition fluxes. Including VOC dry deposition reduces the global
annual-total SOA production rate by 2 %–32 %, with the range
reflecting uncertainties in surface resistances. Including VOC wet deposition
reduces the global annual-total SOA production rate by 15 % and is
relatively insensitive to changes in effective Henry's law coefficients. Without precursor deposition, simulated SOA concentrations are lower than observed
with a normalised mean bias (NMB) of <span class="inline-formula">−51</span> %. Hence, including SOA
precursor deposition worsens model agreement with observations even further
(NMB <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>=</mo><mo>-</mo><mn mathvariant="normal">66</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="ebae49e8c9ad6e6d688665cc5a18beeb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-12-2539-2019-ie00001.svg" width="32pt" height="10pt" src="gmd-12-2539-2019-ie00001.png"/></svg:svg></span></span> %). Secondly, for the anthropogenic and biomass burning VOC
precursors of SOA (VOC<span class="inline-formula"><sub>ANT∕BB</sub></span>), model simulations were performed
by (a) varying the parent hydrocarbon reactivity, (b) varying the number of reaction
intermediates, and (c) accounting for differences in volatility between
oxidation products from various pathways. These changes were compared to a
scheme where VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> adopts the reactivity of a monoterpene
(<span class="inline-formula"><i>α</i></span>-pinene), and is oxidised in a single-step mechanism with a fixed
SOA yield. By using the chemical reactivity of either benzene, toluene, or
naphthalene for VOC<span class="inline-formula"><sub>ANT∕BB</sub></span>, the global annual-total
VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> oxidation rate changes by <span class="inline-formula">−3</span> %, <span class="inline-formula">−31</span> %, or
<span class="inline-formula">−66</span> %, respectively, compared to when using <span class="inline-formula"><i>α</i></span>-pinene. Increasing
the number of reaction intermediates, by introducing a peroxy radical
(<span class="inline-formula">RO<sub>2</sub></span>), slightly slows the rate of SOA formation, but has no impact on
the global annual-total SOA production rate. However, <span class="inline-formula">RO<sub>2</sub></span> undergoes
competitive oxidation reactions, forming products with substantially
different volatilities. Accounting for the differences in product volatility
between <span class="inline-formula">RO<sub>2</sub></span> oxidation pathways increases the global SOA production
rate by 153 % compared to using a single SOA yield. Overall, for
relatively reactive compounds such as toluene and naphthalene, the reduction
in reactivity for VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> oxidation is outweighed by accounting
for the difference in volatility of <span class="inline-formula">RO<sub>2</sub></span> products, leading to a net
increase in the global annual-total SOA production rate of 85 % and
145 %, respectively, and improvements in model agreement (NMB of
<span class="inline-formula">−46</span> % and 56 %, respectively). However, for benzene, the reduction
in VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> oxidation is not outweighed by accounting for the
difference in SOA yield pathways, leading to a small change in the global
annual-total SOA production rate of <span class="inline-formula">−3</span> %, and a slight worsening of
model agreement with observations (NMB <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>=</mo><mo>-</mo><mn mathvariant="normal">77</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="b80a64ae8f3bc6a99fdb018978a614b7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-12-2539-2019-ie00002.svg" width="32pt" height="10pt" src="gmd-12-2539-2019-ie00002.png"/></svg:svg></span></span> %). These results
highlight that variations in both VOC deposition and oxidation mechanisms
contribute to substantial uncertainties in the global SOA budget and model
agreement with observations.</p> |
| first_indexed | 2024-12-12T20:44:55Z |
| format | Article |
| id | doaj.art-5fc2b1d371fa4bc3b204ad91a9698e13 |
| institution | Directory Open Access Journal |
| issn | 1991-959X 1991-9603 |
| language | English |
| last_indexed | 2024-12-12T20:44:55Z |
| publishDate | 2019-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Geoscientific Model Development |
| spelling | doaj.art-5fc2b1d371fa4bc3b204ad91a9698e132022-12-22T00:12:37ZengCopernicus PublicationsGeoscientific Model Development1991-959X1991-96032019-06-01122539256910.5194/gmd-12-2539-2019The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4)J. M. Kelly0J. M. Kelly1R. M. Doherty2F. M. O'Connor3G. W. Mann4H. Coe5D. Liu6School of GeoSciences, The University of Edinburgh, Edinburgh, EH8 9XP, UKnow at: Institute for Data, Systems, and Society, Massachusetts Institute of Technology, Cambridge, MA, USASchool of GeoSciences, The University of Edinburgh, Edinburgh, EH8 9XP, UKMet Office Hadley Centre, Exeter, EX1 3PB, UKNational Centre for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UKCentre for Atmospheric Sciences, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UKCentre for Atmospheric Sciences, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK<p><span id="page2540"/>The representation of volatile organic compound (VOC) deposition and oxidation mechanisms in the context of secondary organic aerosol (SOA) formation are developed in the United Kingdom Chemistry and Aerosol (UKCA) chemistry–climate model. Impacts of these developments on both the global SOA budget and model agreement with observations are quantified. Firstly, global model simulations were performed with varying VOC dry deposition and wet deposition fluxes. Including VOC dry deposition reduces the global annual-total SOA production rate by 2 %–32 %, with the range reflecting uncertainties in surface resistances. Including VOC wet deposition reduces the global annual-total SOA production rate by 15 % and is relatively insensitive to changes in effective Henry's law coefficients. Without precursor deposition, simulated SOA concentrations are lower than observed with a normalised mean bias (NMB) of <span class="inline-formula">−51</span> %. Hence, including SOA precursor deposition worsens model agreement with observations even further (NMB <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>=</mo><mo>-</mo><mn mathvariant="normal">66</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="ebae49e8c9ad6e6d688665cc5a18beeb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-12-2539-2019-ie00001.svg" width="32pt" height="10pt" src="gmd-12-2539-2019-ie00001.png"/></svg:svg></span></span> %). Secondly, for the anthropogenic and biomass burning VOC precursors of SOA (VOC<span class="inline-formula"><sub>ANT∕BB</sub></span>), model simulations were performed by (a) varying the parent hydrocarbon reactivity, (b) varying the number of reaction intermediates, and (c) accounting for differences in volatility between oxidation products from various pathways. These changes were compared to a scheme where VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> adopts the reactivity of a monoterpene (<span class="inline-formula"><i>α</i></span>-pinene), and is oxidised in a single-step mechanism with a fixed SOA yield. By using the chemical reactivity of either benzene, toluene, or naphthalene for VOC<span class="inline-formula"><sub>ANT∕BB</sub></span>, the global annual-total VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> oxidation rate changes by <span class="inline-formula">−3</span> %, <span class="inline-formula">−31</span> %, or <span class="inline-formula">−66</span> %, respectively, compared to when using <span class="inline-formula"><i>α</i></span>-pinene. Increasing the number of reaction intermediates, by introducing a peroxy radical (<span class="inline-formula">RO<sub>2</sub></span>), slightly slows the rate of SOA formation, but has no impact on the global annual-total SOA production rate. However, <span class="inline-formula">RO<sub>2</sub></span> undergoes competitive oxidation reactions, forming products with substantially different volatilities. Accounting for the differences in product volatility between <span class="inline-formula">RO<sub>2</sub></span> oxidation pathways increases the global SOA production rate by 153 % compared to using a single SOA yield. Overall, for relatively reactive compounds such as toluene and naphthalene, the reduction in reactivity for VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> oxidation is outweighed by accounting for the difference in volatility of <span class="inline-formula">RO<sub>2</sub></span> products, leading to a net increase in the global annual-total SOA production rate of 85 % and 145 %, respectively, and improvements in model agreement (NMB of <span class="inline-formula">−46</span> % and 56 %, respectively). However, for benzene, the reduction in VOC<span class="inline-formula"><sub>ANT∕BB</sub></span> oxidation is not outweighed by accounting for the difference in SOA yield pathways, leading to a small change in the global annual-total SOA production rate of <span class="inline-formula">−3</span> %, and a slight worsening of model agreement with observations (NMB <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>=</mo><mo>-</mo><mn mathvariant="normal">77</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="b80a64ae8f3bc6a99fdb018978a614b7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gmd-12-2539-2019-ie00002.svg" width="32pt" height="10pt" src="gmd-12-2539-2019-ie00002.png"/></svg:svg></span></span> %). These results highlight that variations in both VOC deposition and oxidation mechanisms contribute to substantial uncertainties in the global SOA budget and model agreement with observations.</p>https://www.geosci-model-dev.net/12/2539/2019/gmd-12-2539-2019.pdf |
| spellingShingle | J. M. Kelly J. M. Kelly R. M. Doherty F. M. O'Connor G. W. Mann H. Coe D. Liu The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4) Geoscientific Model Development |
| title | The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4) |
| title_full | The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4) |
| title_fullStr | The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4) |
| title_full_unstemmed | The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4) |
| title_short | The roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production: a global perspective using the UKCA chemistry–climate model (vn8.4) |
| title_sort | roles of volatile organic compound deposition and oxidation mechanisms in determining secondary organic aerosol production a global perspective using the ukca chemistry climate model vn8 4 |
| url | https://www.geosci-model-dev.net/12/2539/2019/gmd-12-2539-2019.pdf |
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