Influence of aromatics on tropospheric gas-phase composition

Abstract. Aromatics contribute a significant fraction to organic compounds in the troposphere and are mainly emitted by anthropogenic activities and biomass burning. Their oxidation in lab experiments is known to lead to the formation of ozone and aerosol precursors. However, their overall impact on tropospheric composition is uncertain as it depends on transport, multiphase chemistry, and removal processes of the oxidation intermediates. Representation of aromatics in global atmospheric models has been either neglected or highly simplified. Here, we present an assessment of their impact on gas-phase chemistry, using the general circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry). We employ a comprehensive kinetic model to represent the oxidation of the following monocyclic aromatics: benzene, toluene, xylenes, phenol, styrene, ethylbenzene, trimethylbenzenes, benzaldehyde, and lumped higher aromatics that contain more than nine C atoms. Significant regional changes are identified for several species. For instance, glyoxal increases by 130 % in Europe and 260 % in East Asia, respectively. Large increases in HCHO are also predicted in these regions. In general, the influence of aromatics is particularly evident in areas with high concentrations of NOx, with increases up to 12 % in O3 and 17 % in OH. On a global scale, the estimated net changes of trace gas levels are minor when aromatic compounds are included in our model. For instance, the tropospheric burden of CO increases by about 6 %, while the burdens of OH, O3, and NOx (NO+NO2) decrease between 3 % and 9 %. The global mean changes are small, partially because of compensating effects between high- and low-NOx regions. The largest change is predicted for the important aerosol precursor glyoxal, which increases globally by 36 %. In contrast to other studies, the net change in tropospheric ozone is predicted to be negative, −3 % globally. This change is larger in the Northern Hemisphere where global models usually show positive biases. We find that the reaction with phenoxy radicals is a significant loss for ozone, on the order of 200–300 Tg yr−1, which is similar to the estimated ozone loss due to bromine chemistry. Although the net global impact of aromatics is limited, our results indicate that aromatics can strongly influence tropospheric chemistry on a regional scale, most significantly in East Asia. An analysis of the main model uncertainties related to oxidation and emissions suggests that the impact of aromatics may even be significantly larger.

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Influence of aromatics on tropospheric gas-phase composition

10.5194/acp-2020-461 ◽

2020 ◽

Cited By ~ 1

Author(s):

Domenico Taraborrelli ◽

David Cabrera-Perez ◽

Sara Bacer ◽

Sergey Gromov ◽

Jos Lelieveld ◽

...

Keyword(s):

East Asia ◽

Gas Phase ◽

Atmospheric Chemistry ◽

General Circulation ◽

Anthropogenic Activities ◽

Regional Scale ◽

Circulation Model ◽

Significant Loss ◽

Tropospheric Chemistry ◽

The Impact

Abstract. Aromatics contribute a significant fraction to organic compounds in the troposphere and are mainly emitted by anthropogenic activities and biomass burning. Their oxidation in lab experiments is known to lead to the formation of ozone and aerosol precursors. However, their overall impact on tropospheric composition is uncertain as it depends on transport, multiphase chemistry, and removal processes of the oxidation intermediates. Representation of aromatics in global atmospheric models has been either neglected or highly simplified. Here, we present an assessment of their impact on the gas-phase chemistry, using the general circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry). We employ a comprehensive kinetic model to represent the oxidation of the following monocyclic aromatics: benzene, toluene, xylenes, phenol, styrene, ethylbenzene, trimethylbenzenes, benzaldehyde, and lumped higher aromatics that contain more than 9 C atoms. Significant regional changes are identified for several species. For instance, glyoxal increases by 130 % in Europe and 260 % in East Asia, respectively. Large increases in HCHO are also predicted in these regions. In general, the influence of aromatics is particularly evident in areas with high concentrations of NOx, with increases up to 12 % in O3 and 17 % in OH. On a global scale, the estimated net changes are minor when aromatic compounds are included in our model. For instance, the tropospheric burden of CO increases by about 6 %, while the burdens of OH, O3, and NOx (NO + NO2) decrease between 3 % and 9 %. The global mean changes are small, partially because of compensating effects between high- and low-NOx regions. The largest change is predicted for the important aerosol precursor glyoxal, which increases globally by 36 %. In contrast to other studies, the net change in tropospheric ozone is predicted to be negative, −3 % globally. This change is larger in the northern hemisphere where global models usually show positive biases. We find that the reaction with phenoxy radicals is a significant loss for ozone, of the order of 200–300 Tg/yr, which is similar to the estimated ozone loss due to bromine chemistry. Although the net global impact of aromatics is limited, our results indicate that aromatics can strongly influence tropospheric chemistry on a regional scale, most significantly in East Asia. An analysis of the main model uncertainties related to oxidation and emissions suggests that the impact of aromatics may even be significantly larger.

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Impacts of monocyclic aromatics on regional and global tropospheric gas-phase chemistry

10.5194/egusphere-egu2020-5114 ◽

2020 ◽

Author(s):

Rolf Sander ◽

David Cabrera-Perez ◽

Sara Bacer ◽

Sergey Gromov ◽

Jos Lelieveld ◽

...

Keyword(s):

East Asia ◽

Gas Phase ◽

Aromatic Compounds ◽

General Circulation ◽

Regional Scale ◽

Circulation Model ◽

Tropospheric Chemistry ◽

Chemical Mechanism ◽

Gas Phase Chemistry ◽

Phase Chemistry

Aromatic compounds in the troposphere are reactive towards ozone (O3), hydroxyl (OH) and other radicals. Here we present an assessment of their impacts on the gas-phase chemistry, using the general circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry). The monocyclic aromatics considered in this study comprise benzene, toluene, xylenes, phenol, styrene, ethylbenzene, trimethylbenzenes, benzaldehyde and lumped higher aromatics bearing more than 9 C atoms. On a global scale, the estimated net changes are minor when aromatic compounds are included in the chemical mechanism of our model. For instance, the tropospheric burden of CO increases by about 6 %, and those of OH, O3, and NOx (NO + NO2) decrease between 2 % and 14 %. The global mean changes are small partially because of compensating effects between high- and low-NOx regions. The largest change is predicted for glyoxal, which increases globally by 36 %. Significant regional changes are identified for several species. For instance, glyoxal increases by 130 % in Europe and 260 % in East Asia, respectively. Large increases in HCHO are also predicted in these regions. In general, the influence of aromatics is particularly evident in areas with high concentrations of NOx, with increases up to 12 % in O3 and 17 % in OH. Although the global impact of aromatics is limited, our results indicate that aromatics can strongly influence tropospheric chemistry on a regional scale, most significantly in East Asia.

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Effects of business-as-usual anthropogenic emissions on air quality

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-6915-2012 ◽

2012 ◽

Vol 12 (15) ◽

pp. 6915-6937 ◽

Cited By ~ 51

Author(s):

A. Pozzer ◽

P. Zimmermann ◽

U.M. Doering ◽

J. van Aardenne ◽

H. Tost ◽

...

Keyword(s):

Air Pollution ◽

Air Quality ◽

East Asia ◽

South Asia ◽

Atmospheric Chemistry ◽

General Circulation ◽

Circulation Model ◽

Business As Usual ◽

The Impact ◽

Very High

Abstract. The atmospheric chemistry general circulation model EMAC has been used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies ("business as usual"). This scenario is chosen to show the effects of not implementing legislation to prevent additional climate change and growing air pollution, other than what is in place for the base year 2005, representing a pessimistic (but plausible) future. By comparing with recent observations, it is shown that the model reproduces the main features of regional air pollution distributions though with some imprecisions inherent to the coarse horizontal resolution (~100 km) and simplified bottom-up emission input. To identify possible future hot spots of poor air quality, a multi pollutant index (MPI), suited for global model output, has been applied. It appears that East and South Asia and the Middle East represent such hotspots due to very high pollutant concentrations, while a general increase of MPIs is observed in all populated regions in the Northern Hemisphere. In East Asia a range of pollutant gases and fine particulate matter (PM2.5) is projected to reach very high levels from 2005 onward, while in South Asia air pollution, including ozone, will grow rapidly towards the middle of the century. Around the Persian Gulf, where natural PM2.5 concentrations are already high (desert dust), ozone levels are expected to increase strongly. The population weighted MPI (PW-MPI), which combines demographic and pollutant concentration projections, shows that a rapidly increasing number of people worldwide will experience reduced air quality during the first half of the 21st century. Following this business as usual scenario, it is projected that air quality for the global average citizen in 2050 would be almost comparable to that for the average citizen in East Asia in the year 2005, which underscores the need to pursue emission reductions.

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Effects of business-as-usual anthropogenic emissions on air quality

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-8617-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 8617-8676

Author(s):

A. Pozzer ◽

P. Zimmermann ◽

U.M. Doering ◽

J. van Aardenne ◽

H. Tost ◽

...

Keyword(s):

Air Pollution ◽

Air Quality ◽

East Asia ◽

South Asia ◽

Atmospheric Chemistry ◽

General Circulation ◽

Circulation Model ◽

Business As Usual ◽

The Impact ◽

Very High

Abstract. The atmospheric chemistry general circulation model EMAC has been used to estimate the impact of anthropogenic emission changes on global and regional air quality in recent and future years (2005, 2010, 2025 and 2050). The emission scenario assumes that population and economic growth largely determine energy and food consumption and consequent pollution sources with the current technologies ("business as usual"). This scenario is chosen to show the effects of not implementing legislation to prevent additional climate change and growing air pollution, other than what is in place for the base year 2005, representing a pessimistic (but feasible) future. By comparing with recent observations, it is shown that the model reproduces the main features of regional air pollution distributions though with some imprecisions inherent to the coarse horizontal resolution (~100 km) and simplified bottom-up emission input. To identify possible future hot spots of poor air quality, a multi pollutant index (MPI), suited for global model output, has been applied. It appears that East and South Asia and the Middle East represent such hotspots due to very high pollutant concentrations, although a general increase of MPIs is observed in all populated regions in the Northern Hemisphere. In East Asia a range of pollutant gases and fine particulate matter (PM2.5) is projected to reach very high levels from 2005 onward, while in South Asia air pollution, including ozone, will grow rapidly towards the middle of the century. Around the Arabian Gulf, where natural PM2.5 concentrations are already high (desert dust), ozone levels are expected to increase strongly. The per capita MPI (PCMPI), which combines demographic and pollutants concentrations projections, shows that a rapidly increasing number of people worldwide will experience reduced air quality during the first half of the 21st century. Following the business as usual scenario, it is projected that air quality for the global average citizen in 2050 would be almost comparable to that for the average citizen in the East Asia in the year 2005, which underscores the need to pursue emission reductions.

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Ozone impacts of gas–aerosol uptake in global chemistry transport models

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-3147-2018 ◽

2018 ◽

Vol 18 (5) ◽

pp. 3147-3171 ◽

Cited By ~ 11

Author(s):

Scarlet Stadtler ◽

David Simpson ◽

Sabine Schröder ◽

Domenico Taraborrelli ◽

Andreas Bott ◽

...

Keyword(s):

East Asia ◽

Surface Area ◽

General Circulation ◽

Heterogeneous Reaction ◽

Circulation Model ◽

Photochemical Reactions ◽

Heterogeneous Reactions ◽

Transport Models ◽

Global Pattern ◽

The Impact

Abstract. The impact of six heterogeneous gas–aerosol uptake reactions on tropospheric ozone and nitrogen species was studied using two chemical transport models, the Meteorological Synthesizing Centre-West of the European Monitoring and Evaluation Programme (EMEP MSC-W) and the European Centre Hamburg general circulation model combined with versions of the Hamburg Aerosol Model and Model for Ozone and Related chemical Tracers (ECHAM-HAMMOZ). Species undergoing heterogeneous reactions in both models include N2O5, NO3, NO2, O3, HNO3, and HO2. Since heterogeneous reactions take place at the aerosol surface area, the modelled surface area density (Sa) of both models was compared to a satellite product retrieving the surface area. This comparison shows a good agreement in global pattern and especially the capability of both models to capture the extreme aerosol loadings in east Asia. The impact of the heterogeneous reactions was evaluated by the simulation of a reference run containing all heterogeneous reactions and several sensitivity runs. One reaction was turned off in each sensitivity run to compare it with the reference run. The analysis of the sensitivity runs confirms that the globally most important heterogeneous reaction is the one of N2O5. Nevertheless, NO2, HNO3, and HO2 heterogeneous reactions gain relevance particularly in east Asia due to the presence of high NOx concentrations and high Sa in the same region. The heterogeneous reaction of O3 itself on dust is of minor relevance compared to the other heterogeneous reactions. The impacts of the N2O5 reactions show strong seasonal variations, with the biggest impacts on O3 in springtime when photochemical reactions are active and N2O5 levels still high. Evaluation of the models with northern hemispheric ozone surface observations yields a better agreement of the models with observations in terms of concentration levels, variability, and temporal correlations at most sites when the heterogeneous reactions are incorporated. Our results are loosely consistent with results from earlier studies, although the magnitude of changes induced by N2O5 reaction is at the low end of estimates, which seems to fit a trend, whereby the more recent the study the lower the impacts of these reactions.

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Evaluation of CLaMS, KASIMA and ECHAM5/MESSy1 simulations in the lower stratosphere using observations of Odin/SMR and ILAS/ILAS-II

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-1977-2009 ◽

2009 ◽

Vol 9 (1) ◽

pp. 1977-2020

Author(s):

F. Khosrawi ◽

R. Müller ◽

M. H. Proffitt ◽

R. Ruhnke ◽

O. Kirner ◽

...

Keyword(s):

Atmospheric Chemistry ◽

General Circulation ◽

Lower Stratosphere ◽

Climate Model ◽

Middle Atmosphere ◽

Circulation Model ◽

Lagrangian Model ◽

Data Sets ◽

Data Set ◽

The Impact

Abstract. 1-year data sets of monthly averaged nitrous oxide (N2O) and ozone (O3) derived from satellite measurements were used as a tool for the evaluation of atmospheric photochemical models. Two 1-year data sets, one derived from the Improved Limb Atmospheric Spectrometer (ILAS and ILAS-II) and one from the Odin Sub-Millimetre Radiometer (Odin/SMR) were employed. Here, these data sets are used for the evaluation of two Chemical Transport Models (CTMs), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and the Chemical Lagrangian Model of the Stratosphere (CLaMS) as well as for one Chemistry-Climate Model (CCM), the atmospheric chemistry general circulation model ECHAM5/MESSy1 (E5M1) in the lower stratosphere with focus on the Northern Hemisphere. Since the Odin/SMR measurements cover the entire hemisphere, the evaluation is performed for the entire hemisphere as well as for the low latitudes, midlatitudes and high latitudes using the Odin/SMR 1-year data set as reference. To assess the impact of using different data sets for such an evaluation study we repeat the evaluation for the polar lower stratosphere using the ILAS/ILAS-II data set. Only small differences were found using ILAS/ILAS-II instead of Odin/SMR as a reference, thus, showing that the results are not influenced by the particular satellite data set used for the evaluation. The evaluation of CLaMS, KASIMA and E5M1 shows that all models are in good agreement with Odin/SMR and ILAS/ILAS-II. Differences are generally in the range of ±20%. Larger differences (up to −40%) are found in all models at 500±25 K for N2O mixing ratios greater than 200 ppb. Generally, the largest differences were found for the tropics and the lowest for the polar regions. However, an underestimation of polar winter ozone loss was found both in KASIMA and E5M1 both in the Northern and Southern Hemisphere.

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The influence of the vertical distribution of emissions on tropospheric chemistry

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-16051-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 16051-16083

Author(s):

A. Pozzer ◽

P. Jöckel ◽

J. Van Aardenne

Keyword(s):

Vertical Distribution ◽

Atmospheric Chemistry ◽

General Circulation ◽

Circulation Model ◽

Tropospheric Chemistry ◽

Aircraft Observations ◽

Field Campaigns ◽

The Vertical Distribution ◽

Lower Correlation ◽

Model Layer

Abstract. The atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy atmospheric chemistry) is used to investigate the effect of height dependent emissions on tropospheric chemistry. In a sensitivity simulation, anthropogenic and biomass burning emissions are released in the lowest model layer. The resulting tracer distributions are compared to those of a former simulation applying height dependent emissions. Although the differences between the two simulations in the free troposphere are small (less than 5%), large differences are present in polluted regions at the surface, in particular for NOx (more than 100%) and non-methane hydrocarbons (up to 30%), whereas for OH the differences at the same locations are somewhat lower (15%). Global ozone formation is virtually unaffected by the choice of the vertical distribution of emissions. Nevertheless, local ozone changes can be up to 30%. Model results of both simulations are further compared to observations from field campaigns and to data from measurement stations. The two simulations show no significant differences when compared to aircraft observations. In contrast, for measurements from surface stations, the simulation with emissions in the lowest model layer gives a 20% lower correlation to the observations compared to the simulation with height dependent emissions.

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Methane chemistry in a nutshell – The new submodels CH4 (v1.0) and TRSYNC (v1.0) in MESSy (v2.54.0)

10.5194/gmd-2020-137 ◽

2020 ◽

Author(s):

Franziska Winterstein ◽

Patrick Jöckel

Keyword(s):

Water Vapour ◽

Atmospheric Chemistry ◽

General Circulation ◽

Hydrological Cycle ◽

Circulation Model ◽

Optimization Techniques ◽

Specific Humidity ◽

Climate Projections ◽

Sensitivity Studies ◽

The Impact

Abstract. Climate projections including chemical feedbacks rely on state-of-the-art chemistry-climate models (CCMs). Of particular importance is the role of methane (CH4) for the budget of stratospheric water vapor (SWV), which has an important climate impact. However, simulations with CCMs are, due to the large number of involved chemical species, computationally demanding, which limits the simulation of sensitivity studies. To allow for sensitivity studies and ensemble simulations with a reduced demand for computational resources, we introduce a simpliﬁed approach to simulate the core of methane chemistry in form of the new Modular Earth Submodel System (MESSy) submodel CH4. It involves an atmospheric chemistry mechanism reduced to the sink reactions of CH4 with predeﬁned ﬁelds of the hydroxyl radical (OH), excited oxygen (O(1D)), and chlorine (Cl), as well as photolysis and the reaction products limited to water vapour (H2O). This chemical production of H2O is optionally feed back onto the speciﬁc humidity (q) of the connected General Circulation Model (GCM), to account for the impact onto SWV and its effect on radiation and stratospheric dynamics. The submodel CH4 is further capable of simulating the four most prevalent CH4 isotopologues for carbon and hydrogen (CH4 and CH3D as well as 12CH4 and 13CH4), respectively. Furthermore, the production of deuterated water vapour (HDO) is, similar to the production of H2O in the CH4 oxidation, optionally feed back to the isotopological hydrological cycle simulated by the submodel H2OISO, using the newly developed auxiliary submodel TRSYNC. Moreover, the simulation of a user deﬁned number of diagnostic CH4 age- and emission classes is possible, which output can be used for ofﬂine inverse optimization techniques. The presented approach combines the most important chemical hydrological feedback including the isotopic signatures with the advantages concerning the computational simplicity of a GCM, in comparison to a full featured CCM.

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Distributions and regional budgets of aerosols and their precursors simulated with the EMAC chemistry-climate model

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-961-2012 ◽

2012 ◽

Vol 12 (2) ◽

pp. 961-987 ◽

Cited By ~ 97

Author(s):

A. Pozzer ◽

A. de Meij ◽

K. J. Pringle ◽

H. Tost ◽

U. M. Doering ◽

...

Keyword(s):

North America ◽

East Asia ◽

Atmospheric Chemistry ◽

General Circulation ◽

Climate Model ◽

Temporal Distribution ◽

Circulation Model ◽

Temporal Correlation ◽

Horizontal Resolution ◽

Nitrate Aerosol

Abstract. The new global anthropogenic emission inventory (EDGAR-CIRCE) of gas and aerosol pollutants has been incorporated in the chemistry general circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry). A relatively high horizontal resolution simulation is performed for the years 2005–2008 to evaluate the capability of the model and the emissions to reproduce observed aerosol concentrations and aerosol optical depth (AOD) values. Model output is compared with observations from different measurement networks (CASTNET, EMEP and EANET) and AODs from remote sensing instruments (MODIS and MISR). A good spatial agreement of the distribution of sulfate and ammonium aerosol is found when compared to observations, while calculated nitrate aerosol concentrations show some discrepancies. The simulated temporal development of the inorganic aerosols is in line with measurements of sulfate and nitrate aerosol, while for ammonium aerosol some deviations from observations occur over the USA, due to the wrong temporal distribution of ammonia gas emissions. The calculated AODs agree well with the satellite observations in most regions, while negative biases are found for the equatorial area and in the dust outflow regions (i.e. Central Atlantic and Northern Indian Ocean), due to an underestimation of biomass burning and aeolian dust emissions, respectively. Aerosols and precursors budgets for five different regions (North America, Europe, East Asia, Central Africa and South America) are calculated. Over East-Asia most of the emitted aerosols (precursors) are also deposited within the region, while in North America and Europe transport plays a larger role. Further, it is shown that a simulation with monthly varying anthropogenic emissions typically improves the temporal correlation by 5–10% compared to one with constant annual emissions.

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A fast stratospheric chemistry solver: the E4CHEM submodel for the atmospheric chemistry global circulation model EMAC

Geoscientific Model Development ◽

10.5194/gmd-3-321-2010 ◽

2010 ◽

Vol 3 (1) ◽

pp. 321-328 ◽

Cited By ~ 2

Author(s):

A. J. G. Baumgaertner ◽

P. Jöckel ◽

B. Steil ◽

H. Tost ◽

R. Sander

Keyword(s):

Atmospheric Chemistry ◽

General Circulation ◽

Circulation Model ◽

Reaction Rates ◽

Heterogeneous Reactions ◽

Tropospheric Chemistry ◽

Box Model ◽

Chemical Mechanism ◽

Global Circulation Model ◽

Stratospheric Chemistry

Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) and the atmospheric chemistry box model CAABA are extended by a computationally very efficient submodel for atmospheric chemistry, E4CHEM. It focuses on stratospheric chemistry but also includes background tropospheric chemistry. It is based on the chemistry of MAECHAM4-CHEM and is intended to serve as a simple and fast alternative to the flexible but also computationally more demanding submodel MECCA. In a model setup with E4CHEM, EMAC is now also suitable for simulations of longer time scales. The reaction mechanism contains basic O3, CH4, CO, HOx, NOx, and ClOx gas phase chemistry. In addition, E4CHEM includes optional fast routines for heterogeneous reactions on sulphate aerosols and polar stratospheric clouds (substituting the existing submodels PSC and HETCHEM), and scavenging (substituting the existing submodel SCAV). We describe the implementation of E4CHEM into the MESSy structure of CAABA and EMAC. For some species the steady state in the box model differs by up to 100% when compared to results from CAABA/MECCA due to different reaction rates. After an update of the reaction rates in E4CHEM the mixing ratios in both boxmodel and 3-D model simulations are in satisfactory agreement with the results from a simulation where MECCA with a similar chemistry scheme was employed. Finally, a comparison against a simulation with a more complex and already evaluated chemical mechanism is presented in order to discuss shortcomings associated with the simplification of the chemical mechanism.

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