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Journal ArticleDOI

The second generation regional acid deposition model chemical mechanism for regional air quality modeling

20 Sep 1990-Journal of Geophysical Research (John Wiley & Sons, Ltd)-Vol. 95, Iss: 10, pp 16343-16367
TL;DR: The Regional Acid Deposition Model (RADM2) as discussed by the authors is a state-of-the-art gas phase chemical mechanism for modeling atmospheric chemistry on a regional scale.
Abstract: A state-of-the-art gas phase chemical mechanism for modeling atmospheric chemistry on a regional scale is presented. The second generation Regional Acid Deposition Model (RADM2) gas phase chemical mechanism, like its predecessor RADM1, is highly nonlinear, since predicted ozone, sulfate, nitric acid and hydrogen peroxide concentrations are complicated functions of NO{sub x} and nonmethane hydrocarbon concentrations. The RADM2 chemical mechanism is an upgrade of RADM1 in that (1) three classes of higher alkanes are used instead of one, (2) a more detailed treatment of aromatic chemistry is used, (3) the two higher alkene classes now represent internal and terminal alkenes, (4) ketones and dicarbonyl species are treated as classes distinct from aldehydes, (5) isoprene is now included as an explicit species, and (6) there is a more detailed treatment of peroxy radical-peroxy radical reactions. As a result of these improvements the RADM2 mechanism simulates the concentrations of peroxyacetyl nitrate, HNO3, and H{sub 2}O{sub 2} under a wide variety of environmental conditions. Comparisons of RADM2 mechanism with the RADM1 mechanism predictions and selected environmental chamber experimental results indicate that for typical atmospheric conditions, both mechanisms reliably predict O{sub 3}, sulfate and nitric acid concentrations. The RADM2 mechanism gives lower and presumably moremore » realistic predictions of H{sub 2}O{sub 2} because of its more detailed treatment of peroxy radical-peroxy radical reactions.« less
Citations
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Journal ArticleDOI
TL;DR: The WRF/Chem model is statistically better skilled in forecasting O3 than MM5/Chem, with no appreciable differences between models in terms of bias with the observations, and consistently exhibits better skill at forecasting the O3 precursors CO and NOy at all of the surface sites.

2,709 citations


Cites methods from "The second generation regional acid..."

  • ...In order to adhere to the RADM2 mechanism, reactivity weighting of the various NAPAPlumped VOC species is used to derive the emissions of ARTICLE IN PRESS G.A. Grell et al. the RADM2-lumped species according to Stockwell et al. (1990, 1997)....

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  • ...This atmospheric chemical mechanism was originally developed by Stockwell et al. (1990) for the Regional Acid Deposition Model, version 2 (RADM2 Chang et al., 1989)....

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  • ...The absorption cross-sections and the quantum yields for the calculation of Jgas are given by Stockwell et al. (1990)....

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  • ...Since we currently use the RADM2 mechanism (Stockwell et al., 1990) in WRF/Chem, the biogenic precursors and their resulting particle concentrations are set to zero....

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Journal ArticleDOI
TL;DR: The Models-3 CMAQ system as mentioned in this paper is a community multiscale air quality modeling system that includes a meteorological modeling system for the description of atmospheric states and motions, emission models for man-made and natural emissions that are injected into the atmosphere, and a chemistry-transport modelling system for simulation of the chemical transformation and fate.
Abstract: This article describes the governing equations, computational algorithms, and other components entering into the Community Multiscale Air Quality (CMAQ) modeling system. This system has been designed to approach air quality as a whole by including state-ofthe-science capabilities for modeling multiple air quality issues, including tropospheric ozone, fine particles, acid deposition, and visibility degradation. CMAQ was also designed to have multiscale capabilities so that separate models were not needed for urban and regional scale air quality modeling. By making CMAQ a modeling system that addresses multiple pollutants and different spatial scales, it has a “one-atmosphere” perspective that combines the efforts of the scientific community. To implement multiscale capabilities in CMAQ, several issues (such as scalable atmospheric dynamics and generalized coordinates), which depend on the desired model resolution, are addressed. A set of governing equations for compressible nonhydrostatic atmospheres is available to better resolve atmospheric dynamics at smaller scales. Because CMAQ is designed to handle scale-dependent meteorological formulations and a large amount of flexibility, its governing equations are expressed in a generalized coordinate system. This approach ensures consistency between CMAQ and the meteorological modeling system. The generalized coordinate system determines the necessary grid and coordinate transformations, and it can accommodate various vertical coordinates and map projections. The CMAQ modeling system simulates various chemical and physical processes that are thought to be important for understanding atmospheric trace gas transformations and distributions. The modeling system contains three types of modeling components (Models-3): a meteorological modeling system for the description of atmospheric states and motions, emission models for man-made and natural emissions that are injected into the atmosphere, and a chemistry-transport modeling system for simulation of the chemical transformation and fate. The chemical transport model includes the following process modules: horizontal advection, vertical advection, mass conservation adjustments for advection processes, horizontal diffusion, vertical diffusion, gas-phase chemical reactions and solvers, photolytic rate computation, aqueous-phase reactions and cloud mixing, aerosol dynamics, size distributions and chemistry, plume chemistry effects, and gas and aerosol deposition velocity estimation. This paper describes the Models-3 CMAQ system, its governing equations, important science algorithms, and a few application examples. This review article cites 114 references. DOI: 10.1115/1.2128636

1,993 citations


Cites background from "The second generation regional acid..."

  • ...[77] and SAPRC99 [44] mechanisms....

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  • ...RADM2 is a lumped species mechanism that uses a reactivity-based weighting scheme to account for lumping chemical compounds into surrogate species [77]....

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Journal ArticleDOI
TL;DR: In this paper, photochemical mechanisms for the atmospheric reactions of 118 VOCs were used to calculate their effects on ozone formation under various NOx conditions in model scenarios representing 39 different urban areas.
Abstract: This paper discusses methods for ranking photochemical ozone formation reactivities of volatile organic compounds (VOCs). Photochemical mechanisms for the atmospheric reactions of 118 VOCs were used to calculate their effects on ozone formation under various NOx conditions in model scenarios representing 39 different urban areas. Their effects on ozone were used to derive 18 different ozone reactivity scales, one of which is the Maximum Incremental Reactivity (MIR) scale used in the new California Low Emission Vehicle and Clean Fuel Regulations. These scales are based on three different methods for quantifying ozone impacts and on six different approaches for dealing with the dependencies of reactivity on NOx. The predictions of the scales are compared, the reasons for their similarities and differences are discussed, and the sensitivities of the scales to NOx and other scenario conditions are examined. Scales based on peak ozone levels were highly dependent on NOx, but those based on integrated ...

1,236 citations

Journal ArticleDOI
TL;DR: The Regional Atmospheric Chemistry Mechanism (RACM) as discussed by the authors is a gas-phase chemical mechanism for the modeling of regional atmospheric chemistry, the mechanism is intended to be valid for remote to polluted conditions and from the Earth's surface through the upper troposphere.
Abstract: A new gas-phase chemical mechanism for the modeling of regional atmospheric chemistry, the “Regional Atmospheric Chemistry Mechanism” (RACM) is presented. The mechanism is intended to be valid for remote to polluted conditions and from the Earth's surface through the upper troposphere. The RACM mechanism is based upon the earlier Regional Acid Deposition Model, version 2 (RADM2) mechanism [Stockwell et al., 1990] and the more detailed Euro-RADM mechanism [Stockwell and Kley, 1994]. The RACM mechanism includes rate constants and product yields from the most recent laboratory measurements, and it has been tested against environmental chamber data. A new condensed reaction mechanism is included for biogenic compounds: isoprene, α-pinene, and d-limonene. The branching ratios for alkane decay were reevaluated, and in the revised mechanism the aldehyde to ketone ratios were significantly reduced. The relatively large amounts of nitrates resulting from the reactions of unbranched alkenes with NO3 are now included, and the production of HO from the ozonolysis of alkenes has a much greater yield. The aromatic chemistry has been revised through the use of new laboratory data. The yield of cresol production from aromatics was reduced, while the reactions of HO, NO3, and O3 with unsaturated dicarbonyl species and unsaturated peroxynitrate are now included in the RACM mechanism. The peroxyacetyl nitrate chemistry and the organic peroxy radical-peroxy radical reactions were revised, and organic peroxy radical +NO3 reactions were added.

960 citations


Cites background or methods or result from "The second generation regional acid..."

  • ...of this paper is to present a completely revised version of the mechanism of Stockwell et al. [1990] and to show the effect of...

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  • ...The RACM mechanism is based upon the earlier Regional Acid Deposition Model, version 2 (RADM2) mechanism [Stockwell et al., 1990] and the more detailed Euro-RADM mechanism [Stockwell and Kley, 1994]....

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  • ...The oxidation mechanism for isoprene, oz-pinene, and d-limonene is much more detailed and realistic than that in the RADM2 mechanism [Stockwell et al., 1990]....

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  • ...Experiment EC-237 is a “benchmark” case that has been presented by several mechanism developers [McRae et al., 1982; Lurmann et al., 1986; Stockwell et al., 1990]....

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  • ...simulations were performed for typical rural and urban conditions in a manner similar to a comparison of the first and second version of the RADM mechanisms [Stockwell et al., 1990]....

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Journal ArticleDOI
TL;DR: Air pollutants consist of a complex combination of gases and particulate matter, which is emitted directly into the atmosphere or formed in the atmosphere through gas-to-particle conversion (secondary) (Figure 1).
Abstract: Urban air pollution represents one of the greatest environmental challenges facing mankind in the 21st century. Noticeably, many developing countries, such as China and India, have experienced severe air pollution because of their fast-developing economy and urbanization. Globally, the urbanization trend is projected to continue: 70% of the world population will reside in urban centers by 2050, and there will exist 41 megacities (with more than 10 million inhabitants) by 2030. Air pollutants consist of a complex combination of gases and particulate matter (PM). In particular, fine PM (particles with the aerodynamic diameter smaller than 2.5 μm or PM_(2.5)) profoundly impacts human health, visibility, the ecosystem, the weather, and the climate, and these PM effects are largely dependent on the aerosol properties, including the number concentration, size, and chemical composition. PM is emitted directly into the atmosphere (primary) or formed in the atmosphere through gas-to-particle conversion (secondary) (Figure 1). Also, primary and secondary PM undergoes chemical and physical transformations and is subjected to transport, cloud processing, and removal from the atmosphere.

931 citations

References
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Journal ArticleDOI
TL;DR: The current knowledge of the gas phase reactions occurring in the troposphere for alkanes, alkenes, alkynes, oxygenates and aromatic hydrocarbons and their photooxidation products is reviewed, and areas of uncertainty identified as mentioned in this paper.

1,149 citations

Journal ArticleDOI
TL;DR: In this paper, a new chemical kinetics mechanism for simulating urban and regional photochemistry has been developed and evaluated, called the Carbon Bond Mechanism IV (CBM-IV), by condensing a detailed mechanism that included the most recent kinetic, mechanistic, and photolytic information.
Abstract: A new chemical kinetics mechanism for simulating urban and regional photochemistry has been developed and evaluated. The mechanism, called the Carbon Bond Mechanism IV (CBM-IV), was derived by condensing a detailed mechanism that included the most recent kinetic, mechanistic, and photolytic information. The CBM-IV contains extensive improvements to earlier carbon bond mechanisms in the chemical representations of aromatics, biogenic hydrocarbons, peroxyacetyl nitrates, and formaldehyde. The performance of the CBM-IV was evaluated against data from 170 experiments conducted in three different smog chambers. These experiments included NOx-air irradiations of individual organic compounds as well as a number of simple and complex organic mixtures. The results of the evaluation indicate substantial improvement in the ability of the CBM-IV to simulate aromatic and isoprene systems with average overcalculation of ozone concentrations of 1% for the aromatic simulations and 6% for the isoprene simulations. The mechanism also performed well in simulating organic mixture experiments. Maximum ozone concentrations calculated for 68 of these experiments were approximately 2% greater than the observed values while formaldehyde values were low by 9%.

1,117 citations

Journal ArticleDOI
TL;DR: In this paper, the delta-Eddington approximation was used to calculate monochromatic radiative fluxes in an absorbing-scattering atmosphere, by combining a Dirac delta function and a two-term approximation, which overcomes the poor accuracy of the Eddington approximation for highly asymmetric phase functions.
Abstract: This paper presents a rapid yet accurate method, the “delta-Eddington” approximation, for calculating monochromatic radiative fluxes in an absorbing-scattering atmosphere. By combining a Dirac delta function and a two-term approximation, it overcomes the poor accuracy of the Eddington approximation for highly asymmetric phase functions. The fraction of scattering into the truncated forward peak is taken proportional to the square of the phase function asymmetry factor, which distinguishes the delta-Eddington approximation from others of similar nature. Comparisons of delta-Eddington albedos, transnmissivities and absorptivities with more exact calculations reveal typical differences of 0–0.022 and maximum differences of 0.15 over wide ranges of optical depth, sun angle, surface albedo, single-scattering albedo and phase function asymmetry. Delta-Eddington fluxes are in error, on the average, by no more than 0.5%0, and at the maximum by no more than 2% of the incident flux. This computationally fa...

1,075 citations

Journal ArticleDOI
TL;DR: In this paper, a three-dimensional Eulerian regional acid deposition model is developed to calculate episodic chemical concentrations and dry and wet deposition of acids in North America using temporally and spatially varying meteorology.
Abstract: We have developed a three-dimensional Eulerian regional acid deposition model to calculate episodic chemical concentrations and dry and wet deposition of acids in North America. This transport, transformation, and deposition modeling system subdivides the troposphere over the eastern United States, southeastern Canada, and the western Atlantic Ocean into a six-level, 30 by 30 horizontal grid with a horizontal grid size of 80 x 80 km/sup 2/. Transport and vertical diffusion of 24 trace gases and particles are calculated using temporally and spatially varying meteorology, provided by a mesoscale meteorological model. A gas phase chemical reaction mechanism is used to simulate concentrations and chemical conversion rates for 36 species, including 14 stable organics and 11 short-lived radicals. Altitude-, latitude-, and season-dependent photolysis rates for nine reactions in the chemical mechanism are specified using a delta-Eddington radiative transfer model which includes O/sub 2/ and O/sub 3/ absorption, scattering and absorption by clouds and aerosols, Rayleigh scattering, and ground relections.

866 citations