scholarly journals Changes to simulated global atmospheric composition resulting from recent revisions to isoprene oxidation chemistry

2021 ◽  
Vol 244 ◽  
pp. 117914
Author(s):  
M. Anwar H. Khan ◽  
Billie-Louise Schlich ◽  
Michael E. Jenkin ◽  
Michael C. Cooke ◽  
Richard G. Derwent ◽  
...  
Keyword(s):  
Atmospheric Composition ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry

scholarly journals Isoprene oxidation mechanisms: measurements and modelling of OH and HO<sub>2</sub> over a South-East Asian tropical rainforest during the OP3 field campaign

2011 ◽  
Vol 11 (3) ◽  
pp. 10343-10401 ◽  
Author(s):  
D. Stone ◽  
M. J. Evans ◽  
P. M. Edwards ◽  
R. Commane ◽  
T. Ingham ◽  
...  
Keyword(s):  
Tropical Rainforest ◽  
Geometric Mean ◽  
Atmospheric Composition ◽  
Peroxy Radicals ◽  
Unimolecular Decomposition ◽  
The Standard Model ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry ◽  
Oxidation Mechanisms

Abstract. Forests are the dominant source of volatile organic compounds into the atmosphere, with isoprene being the most significant species. The oxidation chemistry of these compounds is a significant driver of local, regional and global atmospheric composition. Observations made over Borneo during the OP3 project in 2008, together with an observationally constrained box model are used to assess our understanding of this oxidation chemistry. In line with previous work in tropical forests, we find that the standard model based on MCM chemistry significantly underestimates the observed OH concentrations. Geometric mean observed to modelled ratios of OH and HO2 in airmasses impacted with isoprene are 5.32−4.43+3.68 and 1.18−0.30+0.30 respectively, with 68% of the observations being within the specified variation. We implement a variety of mechanistic changes into the model, including epoxide formation and unimolecular decomposition of isoprene peroxy radicals, and assess their impact on the model success. We conclude that none of the current suggestions can simultaneously remove the bias from both OH and HO2 simulations and believe that detailed laboratory studies are now needed to resolve this issue.

scholarly journals Isoprene oxidation mechanisms: measurements and modelling of OH and HO<sub>2</sub> over a South-East Asian tropical rainforest during the OP3 field campaign

2011 ◽  
Vol 11 (13) ◽  
pp. 6749-6771 ◽  
Author(s):  
D. Stone ◽  
M. J. Evans ◽  
P. M. Edwards ◽  
R. Commane ◽  
T. Ingham ◽  
...  
Keyword(s):  
Tropical Rainforest ◽  
Geometric Mean ◽  
Atmospheric Composition ◽  
Peroxy Radicals ◽  
Unimolecular Decomposition ◽  
The Standard Model ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry ◽  
Oxidation Mechanisms

Abstract. Forests are the dominant source of volatile organic compounds into the atmosphere, with isoprene being the most significant species. The oxidation chemistry of these compounds is a significant driver of local, regional and global atmospheric composition. Observations made over Borneo during the OP3 project in 2008, together with an observationally constrained box model are used to assess our understanding of this oxidation chemistry. In line with previous work in tropical forests, we find that the standard model based on MCM chemistry significantly underestimates the observed OH concentrations. Geometric mean observed to modelled ratios of OH and HO2 in airmasses impacted with isoprene are 5.32−4.43+3.68 and 1.18−0.30+0.30 respectively, with 68 % of the observations being within the specified variation. We implement a variety of mechanistic changes into the model, including epoxide formation and unimolecular decomposition of isoprene peroxy radicals, and assess their impact on the model success. We conclude that none of the current suggestions can simultaneously remove the bias from both OH and HO2 simulations and believe that detailed laboratory studies are now needed to resolve this issue.

scholarly journals Investigation of a potential HCHO measurement artifact from ISOPOOH

2016 ◽  
Vol 9 (9) ◽  
pp. 4561-4568 ◽  
Author(s):  
Jason M. St. Clair ◽  
Jean C. Rivera-Rios ◽  
John D. Crounse ◽  
Eric Praske ◽  
Michelle J. Kim ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Laboratory Experiments ◽  
First Generation ◽  
Atmospheric Composition ◽  
Previous Exposure ◽  
Methyl Vinyl ◽  
Isoprene Oxidation ◽  
Measurement Artifact ◽  
Recent Laboratory

Abstract. Recent laboratory experiments have shown that a first generation isoprene oxidation product, ISOPOOH, can decompose to methyl vinyl ketone (MVK) and methacrolein (MACR) on instrument surfaces, leading to overestimates of MVK and MACR concentrations. Formaldehyde (HCHO) was suggested as a decomposition co-product, raising concern that in situ HCHO measurements may also be affected by an ISOPOOH interference. The HCHO measurement artifact from ISOPOOH for the NASA In Situ Airborne Formaldehyde instrument (ISAF) was investigated for the two major ISOPOOH isomers, (1,2)-ISOPOOH and (4,3)-ISOPOOH, under dry and humid conditions. The dry conversion of ISOPOOH to HCHO was 3 ± 2 % and 6 ± 4 % for (1,2)-ISOPOOH and (4,3)-ISOPOOH, respectively. Under humid (relative humidity of 40–60 %) conditions, conversion to HCHO was 6 ± 4 % for (1,2)-ISOPOOH and 10 ± 5 % for (4,3)-ISOPOOH. The measurement artifact caused by conversion of ISOPOOH to HCHO in the ISAF instrument was estimated for data obtained on the 6 September 2013 flight of the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. Prompt ISOPOOH conversion to HCHO was the source of < 4 % of the observed HCHO, including in the high-isoprene boundary layer. Time-delayed conversion, where previous exposure to ISOPOOH affects measured HCHO later in the flight, was conservatively estimated to be < 10 % of observed HCHO, and is significant only when high ISOPOOH sampling periods immediately precede periods of low HCHO.

scholarly journals Improved simulation of isoprene oxidation chemistry with the ECHAM5/MESSy chemistry-climate model: lessons from the GABRIEL airborne field campaign

2008 ◽  
Vol 8 (2) ◽  
pp. 6273-6312 ◽  
Author(s):  
T. M. Butler ◽  
D. Taraborrelli ◽  
C. Brühl ◽  
H. Fischer ◽  
H. Harder ◽  
...  
Keyword(s):  
Rate Constant ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Effective Rate Constant ◽  
Effective Rate ◽  
Current Generation ◽  
Mixing Ratios ◽  
Oxidation Chain ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry

Abstract. The GABRIEL airborne field measurement campaign, conducted over the Guyanas in October 2005, produced measurements of hydroxyl radical (OH) concentration which are significantly higher than can be simulated using current generation models of atmospheric chemistry. Based on the hypothesis that this "missing OH" is due to an as-yet undiscovered mechanism for recycling OH during the oxidation chain of isoprene, we determine that an OH recycling of about 40–50% (compared with 5–10% in current generation isoprene oxidation mechanisms) is necessary in order for our modelled OH to approach the lower error bounds of the OH observed during GABRIEL. Such a large amount of OH in our model leads to unrealistically low mixing ratios of isoprene. In order for our modelled isoprene mixing ratios to match those observed during the campaign, we also require that the effective rate constant for the reaction of isoprene with OH be reduced by about 50% compared with the lower bound of the range recommended by IUPAC. We show that a reasonable explanation for this lower effective rate constant could be the segregation of isoprene and OH in the mixed layer. Our modelling results are consistent with a global, annual isoprene source of about 500 Tg(C) yr−1, allowing experimentally derived and established isoprene flux rates to be reconciled with global models.

scholarly journals Understanding the impact of recent advances in isoprene photooxidation on simulations of regional air quality

2012 ◽  
Vol 12 (10) ◽  
pp. 27173-27218 ◽  
Author(s):  
Y. Xie ◽  
F. Paulot ◽  
W. P. L. Carter ◽  
C. G. Nolte ◽  
D. J. Luecken ◽  
...  
Keyword(s):  
Air Quality ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Chemical Mechanism ◽  
Recent Advances ◽  
Dry Deposition Velocity ◽  
Isoprene Nitrates ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry ◽  
The Impact

Abstract. The CMAQ model in combination with observations for INTEX-NA/ICARTT 2004 are used to evaluate recent advances in isoprene oxidation chemistry and provide constraints on isoprene nitrate yields, isoprene nitrate lifetimes, and NOx recycling rates. We incorporate recent advances in isoprene oxidation chemistry into the SAPRC-07 chemical mechanism within the US EPA Community Multiscale Air Quality (CMAQ) model. The results show improved model performance for a range of species compared against aircraft observations from the INTEX-NA/ICARTT 2004 field campaign. We further investigate the key processes in isoprene nitrate chemistry and evaluate the impact of uncertainties in the isoprene nitrate yield, NOx (NOx = NO + NO2) recycling efficiency, dry deposition velocity, and RO2 + HO2 reaction rates. We focus our examination in the Southeastern United States, which is impacted by both abundant isoprene emissions and high levels of anthropogenic pollutants. We find that NOx concentrations increase by 4–9% as a result of reduced removal by isoprene nitrate chemistry. O3 increases by 2 ppbv as a result of changes in NOx. OH concentrations increase by 30%, which can be primarily attributed to greater HOx production. We find that the model can capture observed total alkyl and multifunctional nitrates (∑ANs) and their relationship with O3, by assuming either an isoprene nitrate yield of 6% and daytime lifetime of 6 h or a yield of 12% and lifetime of 4 h. Uncertainties in the isoprene nitrates can impact ozone production by 10% and OH concentrations by 6%. The uncertainties in NOx recycling efficiency appear to have larger effects than uncertainties in isoprene nitrate yield and dry deposition velocity. Further progress depends on improved understanding of isoprene oxidation pathways, the rate of NOx recycling from isoprene nitrates, and the fate of the secondary, tertiary, and further oxidation products of isoprene.

scholarly journals Chemistry and deposition in the Model of Atmospheric composition at Global and Regional scales using Inversion Techniques for Trace gas Emissions (MAGRITTE v1.1) – Part 1: Chemical mechanism

2019 ◽  
Vol 12 (6) ◽  
pp. 2307-2356 ◽  
Author(s):  
Jean-François Müller ◽  
Trissevgeni Stavrakou ◽  
Jozef Peeters
Keyword(s):  
Chemical Degradation ◽  
Chemical Mechanism ◽  
Atmospheric Composition ◽  
Trace Gas ◽  
Oh Radicals ◽  
Gas Emissions ◽  
Trace Gas Emissions ◽  
Southeastern Us ◽  
Isoprene Oxidation ◽  
Inversion Techniques

Abstract. A new chemical mechanism for the oxidation of biogenic volatile organic compounds (BVOCs) is presented and implemented in the Model of Atmospheric composition at Global and Regional scales using Inversion Techniques for Trace gas Emissions (MAGRITTE v1.1). With a total of 105 organic species and over 265 gas-phase reactions, 69 photodissociations, and 7 heterogeneous reactions, the mechanism treats the chemical degradation of isoprene – its main focus – as well as acetaldehyde, acetone, methylbutenol, and the family of monoterpenes. Regarding isoprene, the mechanism incorporates a state-of-the-art representation of its oxidation scheme accounting for all major advances put forward in recent theoretical and laboratory studies. The recycling of OH radicals in isoprene oxidation through the isomerization of Z-δ-hydroxyperoxy radicals is found to enhance OH concentrations by up to 40 % over western Amazonia in the boundary layer and by 10 %–15 % over the southeastern US and Siberia in July. The model and its chemical mechanism are evaluated against the suite of chemical measurements from the SEAC4RS (Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys) airborne campaign, demonstrating a good overall agreement for major isoprene oxidation products, although the aerosol hydrolysis of tertiary and non-tertiary nitrates remain poorly constrained. The comparisons for methylnitrate indicate a very low nitrate yield (<3×10-4) in the CH3O2+NO reaction. The oxidation of isoprene, acetone, and acetaldehyde by OH is shown to be a substantial source of enols and keto-enols, primarily through the photolysis of multifunctional carbonyls generated in their oxidation schemes. Oxidation of those enols by OH radicals constitutes a sizable source of carboxylic acids estimated at 9 Tg (HC(O)OH) yr−1 and 11 Tg(CH3C(O)OH) yr−1 or ∼20 % of their global identified source. The ozonolysis of alkenes is found to be a smaller source of HC(O)OH (6 Tg HC(O)OH yr−1) than previously estimated, due to several factors including the strong deposition sink of hydroxymethyl hydroperoxide (HMHP).

scholarly journals Sensitivity of tropospheric loads and lifetimes of short lived pollutants to fire emissions

2015 ◽  
Vol 15 (6) ◽  
pp. 3543-3563 ◽  
Author(s):  
N. Daskalakis ◽  
S. Myriokefalitakis ◽  
M. Kanakidou
Keyword(s):  
Biomass Burning ◽  
Atmospheric Transport ◽  
Feedback Mechanism ◽  
Oxidation Products ◽  
Atmospheric Composition ◽  
Secondary Aerosol ◽  
Fire Emissions ◽  
Calculated Load ◽  
Isoprene Oxidation ◽  
Aerosol Emissions

Abstract. The capability of global chemistry and transport models (CTMs) to simulate atmospheric composition and its spatial and temporal changes highly relies on the input data used by the models, in particular the emission inventories. Biomass burning emissions show large spatial, diurnal, seasonal and year-to-year variability. In the present study, we applied a global 3-D CTM to evaluate uncertainties in the computed atmospheric composition associated with the use of different biomass burning emissions and identify areas where observational data can help to reduce these uncertainties. We find the emission inventory choice to lead to regional differences in the calculated load of aerosols up to a factor of 4. Assumptions on the injection height of the biomass burning emissions are found to produce regionally up to 30% differences in the calculated tropospheric lifetimes of pollutants. Computed changes in lifetimes point to a strong chemical feedback mechanism between emissions from biomass burning and isoprene emissions from vegetation that are linked via NOx-driven oxidant chemistry, NOx-dependent changes in isoprene oxidation products, aerosol emissions and atmospheric transport. These interactions reduce isoprene load in the presence of biomass burning emissions by 15%, calculated for the same amount of isoprene emitted into the troposphere. Thus, isoprene load and lifetime are inversely related to the quantities of pollutants emitted by biomass burning. These interactions are shown to be able to increase the global annual secondary aerosol yield from isoprene emissions, defined as the ratio of tropospheric loads of secondary aerosol from isoprene oxidation to isoprene emissions, by up to 18%.

scholarly journals Investigation of a potential HCHO measurement artifact from ISOPOOH

2016 ◽  
Author(s):  
Jason M. St. Clair ◽  
Jean C. Rivera-Rios ◽  
John D. Crounse ◽  
Eric Praske ◽  
Michelle J. Kim ◽  
...  
Keyword(s):  
Oxidation Product ◽  
Laboratory Experiments ◽  
First Generation ◽  
Vinyl Ketone ◽  
Atmospheric Composition ◽  
Methyl Vinyl ◽  
Isoprene Oxidation ◽  
Measurement Artifact ◽  
Recent Laboratory

Abstract. Recent laboratory experiments have shown that a first generation isoprene oxidation product, ISOPOOH, can decompose to methyl vinyl ketone (MVK) and methacrolein (MACR) on instrument surfaces, leading to overestimates of MVK and MACR concentrations. Formaldehyde (HCHO) was suggested as a decomposition co-product, raising concern that in situ HCHO measurements may also be affected by an ISOPOOH interference. The HCHO measurement artifact from ISOPOOH for the NASA In Situ Airborne Formaldehyde instrument (ISAF) was investigated for the two major ISOPOOH isomers, (1,2)-ISOPOOH and (4,3)-ISOPOOH, under dry and humid conditions. The dry conversion of ISOPOOH to HCHO was 3 ± 2 % and 6 ± 4 % for (1,2)-ISOPOOH and (4,3)-ISOPOOH, respectively. Under humid (RH = 40–60 %) conditions, conversion to HCHO was 6 ± 4 % for (1,2)-ISOPOOH and 10 ± 5 % for (4,3)-ISOPOOH. The measurement artifact caused by conversion of ISOPOOH to HCHO in the ISAF instrument was estimated for data obtained on the 2013 September 6 flight of the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. Prompt ISOPOOH conversion to HCHO was the source for

scholarly journals Improved simulation of isoprene oxidation chemistry with the ECHAM5/MESSy chemistry-climate model: lessons from the GABRIEL airborne field campaign

2008 ◽  
Vol 8 (16) ◽  
pp. 4529-4546 ◽  
Author(s):  
T. M. Butler ◽  
D. Taraborrelli ◽  
C. Brühl ◽  
H. Fischer ◽  
H. Harder ◽  
...  
Keyword(s):  
Rate Constant ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Effective Rate Constant ◽  
Effective Rate ◽  
Current Generation ◽  
Mixing Ratios ◽  
Oxidation Chain ◽  
Isoprene Oxidation ◽  
Oxidation Chemistry

Abstract. The GABRIEL airborne field measurement campaign, conducted over the Guyanas in October 2005, produced measurements of hydroxyl radical (OH) concentration which are significantly higher than can be simulated using current generation models of atmospheric chemistry. Based on the hypothesis that this "missing OH" is due to an as-yet undiscovered mechanism for recycling OH during the oxidation chain of isoprene, we determine that an OH recycling of about 40–50% (compared with 5–10% in current generation isoprene oxidation mechanisms) is necessary in order for our modelled OH to approach the lower error bounds of the OH observed during GABRIEL. Such a large amount of OH in our model leads to unrealistically low mixing ratios of isoprene. In order for our modelled isoprene mixing ratios to match those observed during the campaign, we also require that the effective rate constant for the reaction of isoprene with OH be reduced by about 50% compared with the lower bound of the range recommended by IUPAC. We show that a reasonable explanation for this lower effective rate constant could be the segregation of isoprene and OH in the mixed layer. Our modelling results are consistent with a global, annual isoprene source of about 500 Tg(C) yr−1, allowing experimentally derived and established isoprene flux rates to be reconciled with global models.

Recent updates to the atmospheric chemistry modeling of the ECMWF IFS in support to CAMS

2021 ◽  
Author(s):  
Vincent Huijnen ◽  
Jason Williams ◽  
Idir Bouarar ◽  
Sophie Belamari ◽  
Simon Chabrillat ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Stratospheric Ozone ◽  
Tropospheric Chemistry ◽  
Atmospheric Composition ◽  
Aerosol Formation ◽  
Chemistry Modeling ◽  
Forecasting System ◽  
Isoprene Oxidation ◽  
Reactive Gases ◽  
Monitoring Service

&lt;p&gt;The Integrated Forecasting System (IFS) of ECMWF is the core of the Copernicus Atmosphere Monitoring Service (CAMS) which provides global analyses and forecasts of atmospheric composition, namely reactive gases, aerosol and greenhouse gases. With respect to the atmospheric chemistry component, the operational system currently relies on a modified version of the CB05 chemistry scheme for the troposphere, combined with the Cariolle scheme to describe stratospheric ozone. In an alternative, more recent configuration also stratospheric ozone chemistry is included based on the BASCOE chemistry module. Alternative atmospheric chemistry modules which can be employed are based on MOZART and MOCAGE chemistry.&amp;#160;&lt;br&gt;Recently, further revisions to the modified CB05 tropospheric chemistry scheme have been developed, focusing both on inorganic and organic chemistry, with the aim of improving the quality of existing air-quality products, and the development of new products. On major update is a revision of the isoprene oxidation scheme based on those employed in existing chemistry transport models, as well as inclusion of the basic chemistry describing C8 and C9 aromatics degradation.&amp;#160;&lt;br&gt;An example of a new product derived from these updates include a description of global distribution of glyoxal, while this also resulted in an improved modeling of OH recycling particularly over tropical forests. Also we support improved secondary organic aerosol formation due to gaseous anthropogenic, biogenic and biomass burning sources.&lt;br&gt;In this contribution we provide an overview of these revisions, and provide a first quantification of their uncertainties, by comparing products to observations and to those from alternative chemistry modules.&lt;/p&gt;

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