Segregation and chemical reaction rates in air quality models

Hilst, G. R.

doi:10.1016/s1352-2310(98)00101-0

Cited by 12 publications

(5 citation statements)

References 7 publications

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“…stands for the spatial covariance between A and B. The intensity of segregation is a proper measure of the effect of spatial segregation on nonlinear chemical processes (Hilst, 1998) and represents the deviation from a well-mixed environment due to the coupling between dynamics and chemistry (Zhong et al, 2014). For a second-order reaction A+B  C in a heterogeneous system, the rate of formation of C (Vinuesa and de Arellano, 2005) evaluated for the whole volume of air inside the street canyon in the framework of one-box model can be described as follows, (Figure 1d-e).…”

Section: Intensity Of Segregationmentioning

confidence: 99%

Large eddy simulation of reactive pollutants in a deep urban street canyon: Coupling dynamics with O3-NO -VOC chemistry

Zhong

Cai

Bloss

2017

Environmental Pollution

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A large eddy simulation (LES) model coupled with O-NO-VOC chemistry is implemented to simulate the coupled effects of emissions, mixing and chemical pre-processing within an idealised deep (aspect ratio = 2) urban street canyon under a weak wind condition. Reactive pollutants exhibit significant spatial variations in the presence of two vertically aligned unsteady vortices formed in the canyon. Comparison of the LES results from two chemical schemes (simple NO-O chemistry and a more comprehensive Reduced Chemical Scheme (RCS) chemical mechanism) shows that the concentrations of NO and O inside the street canyon are enhanced by approximately 30-40% via OH/HO chemistry. NO, NO, O, OH and HO are chemically consumed, while NO and O (total oxidant) are chemically produced within the canyon environment. Within-canyon pre-processing increases oxidant fluxes from the canyon to the overlying boundary layer, and this effect is greater for deeper street canyons (as found in many traditional European urban centres) than shallower (lower aspect ratio) streets. There is clear evidence of distinct behaviours for emitted chemical species and entrained chemical species, and positive (or negative) values of intensities of segregations are found between pairs of species with similar (or opposite) behaviour. The simplified two-box model underestimated NO and O levels, but overestimated NO levels for both the lower and upper canyon compared with the more realistic LES-chemistry model. This suggests that the segregation effect due to incomplete mixing reduces the chemical conversion rate of NO to NO. This study reveals the impacts of nonlinear O-NO-VOC photochemical processes in the incomplete mixing environment and provides a better understanding of the pre-processing of emissions within canyons, prior to their release to the urban boundary layer, through the coupling of street canyon dynamics and chemistry.

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Section: Intensity Of Segregationmentioning

confidence: 99%

Large eddy simulation of reactive pollutants in a deep urban street canyon: Coupling dynamics with O3-NO -VOC chemistry

Zhong

Cai

Bloss

2017

Environmental Pollution

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“…It is thus argued that errors in the conversion of NO x in fresh biomass burning plumes into the main reservoir species PAN and HNO 3 in coarse resolution models may be substantial. There have been a few studies on the effect of sub‐grid segregation on local ozone production [ Sillman et al , 1990; Chatfield and Delany , 1990; Poppe et al , 1998; Hilst , 1998; Liang and Jacobson , 2000], but none of them investigated the effect on the NO y partitioning, which could exert an important long‐range effect.…”

Section: Nitrogen Speciesmentioning

confidence: 99%

A model for studies of tropospheric ozone and nonmethane hydrocarbons: Model evaluation of ozone‐related species

et al. 2003

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[1] A global three-dimensional model for studies of the tropospheric chemistry of HO x , ozone, and their precursors is thoroughly evaluated with available observations of 15 species from surface stations and/or aircraft campaigns. The effect of grid-resolution was studied by comparing the measurements to model runs at a high ($1.9°Â 1.9°) and a reduced resolution. This study is a follow-up to a previous paper where the model was described and results for ozone were discussed. A statistical analysis of the complete comparison of each species is also presented in order to serve as a quantitative baseline for future evaluations. The seasonality and magnitude of the CO abundance is well simulated except for an overestimate of up to 20 nmol/mol in southern low latitudes. The tropospheric mean methane lifetime is calculated to be 8.7 and 9.1 years for the high-and low-resolution run, respectively, in agreement with recent estimates. Industrial emissions of alkanes from North America appear to be too low in the current data set. Indications for a biogenic source of propane were found by comparing with measurements over the Amazon rain forest. Alkene emissions from oceans are underestimated in the model indicating that they are higher than previous studies suggested. Nitrogen species are mostly reproduced within a factor of 2 or better, but a general bias to underestimate HNO 3 and to overpredict peroxyacetyl nitrate (PAN), especially in remote regions could also be found. NO was well simulated in the lower and mid troposphere, but significantly understimated in the upper troposphere. A sensitivity run shows that studies are needed to better constrain the rate constants for the thermal equilibrium of PAN. Acetone is often underestimated indicating that additional wide-spread sources, likely oceanic, are present. The comparison with other oxygenated species (acetaldehyde, methanol, formic and acetic acid) indicates severe gaps in our understanding of the present budgets of these species. In particular the underestimate of acetaldehyde implies large missing sources (order 100 Tg/yr) of this compound.

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“…This suggests that beyond a certain grid spacing, the coarser the domain resolution, the lower the mixing ratio of predicted ozone. The phenomenon is of interest, because several studies have examined the effects of domain resolution and/or dilution on ozone mixing ratios, ozone production, or ozone production efficiency [e.g., Chatfield and Delany, 1990; Sillman et al, 1990;Jang et al, 1995;Poppe et al, 1998;Hilst, 1998;Liang and Jacobson, 2000]. Jang et al [1995], for example, found that increasing domain resolution could increase or decrease modeled ozone at specific locations.…”

Section: The Effects Of Nestingmentioning

confidence: 99%

GATOR‐GCMM: 2. A study of daytime and nighttime ozone layers aloft, ozone in national parks, and weather during the SARMAP field campaign

Jacobson¹

2001

J. Geophys. Res.

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Abstract. The GATORG-GCMM global-through urban-scale nested air pollution/weather forecast model was applied to study ozone layers aloft, ozone in national parks, and weather during the August 3-6, 1990, SARMAP field campaign in northem and central California. Predictions of meteorological variables and mixing ratios of 20 gases were compared with observations. With nesting, the normalized gross error in predicted near-surface Kelvin temperatures was 1.02% and that in near-surface ozone above 50 ppbv was 22.5%. Statistics from outer nested domains indicated that the coarser the grid spacing, the greater the underprediction of ozone. In the absence of nesting, statistics deteriorated but not a lot. The model-simulated observed nighttime ozone layers aloft and daytime ozone mixed layers in the San Joaquin Valley and San Francisco Bay Area. It also simulated observed daytime and nighttime ozone layers aloft over the San Francisco Bay near Hayward. The formation mexhanism of these layers is discussed. The model was used to estimate that about 47-57% of peak daytime ozone in Sequoia and Yosemite National Parks during SARMAP was produced by anthropogenic gases, 13-3% was produced by biogenic hydrocarbons, and the rest (about 40%) was background.

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Segregation and chemical reaction rates in air quality models

Cited by 12 publications

References 7 publications

Large eddy simulation of reactive pollutants in a deep urban street canyon: Coupling dynamics with O3-NO -VOC chemistry

Large eddy simulation of reactive pollutants in a deep urban street canyon: Coupling dynamics with O3-NO -VOC chemistry

A model for studies of tropospheric ozone and nonmethane hydrocarbons: Model evaluation of ozone‐related species

GATOR‐GCMM: 2. A study of daytime and nighttime ozone layers aloft, ozone in national parks, and weather during the SARMAP field campaign

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