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1
Ainslie, B., and D. G. Steyn. "A scaling analysis of ozone photochemistry." Atmospheric Chemistry and Physics 6, no. 12 (September 11, 2006): 4067–77. http://dx.doi.org/10.5194/acp-6-4067-2006.
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Abstract. A scaling analysis has been used to capture the integrated behaviour of several photochemical mechanisms for a wide range of precursor concentrations and a variety of environmental conditions. The Buckingham Pi method of dimensional analysis was used to express the relevant variables in terms of dimensionless groups. These grouping show maximum ozone, initial NOx and initial VOC concentrations are made non-dimensional by the average NO2 photolysis rate (jav) and the rate constant for the NO–O3 titration reaction (kNO); temperature by the NO–O3 activation energy (ENO) and Boltzmann constant (k) and total irradiation time by the cumulative javΔt photolysis rate. The analysis shows dimensionless maximum ozone concentration can be described by a product of powers of dimensionless initial NOx concentration, dimensionless temperature, and a similarity curve directly dependent on the ratio of initial VOC to NOx concentration and implicitly dependent on the cumulative NO2 photolysis rate. When Weibull transformed, the similarity relationship shows a scaling break with dimensionless model output clustering onto two straight line segments, parameterized using four variables: two describing the slopes of the line segments and two giving the location of their intersection. A fifth parameter is used to normalize the model output. The scaling analysis, similarity curve and parameterization appear to be independent of the details of the chemical mechanism, hold for a variety of VOC species and mixtures and a wide range of temperatures and actinic fluxes.
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Xie, Wenda, Ting Shi, Bing Ge, and Shusheng Zang. "Effects of scaling laws on flow and combustion characteristics of lean premixed swirl burners." Journal of the Global Power and Propulsion Society 6 (December 20, 2022): 343–53. http://dx.doi.org/10.33737/jgpps/156121.
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Modern heavy gas turbine combustors are always huge, so it is difficult and costly to do experiment. Thus, geometry scaling method has come into sight. In this paper, based on a single lean premixed swirl burner, validated computational fluid dynamic (CFD) model was used to study the effects of different scaling laws on various scalling models from 1/2 to 1/10. Experimental study on prototype combustor and the 3/5 scale model under full operating condition is also carried out to verify the NOx emission under different laws. Results showed that DaI scaling law was able to maintain good similarity under combustion state when scaling factor = 1/2–1/5, while Re scaling law would bring significant changes on flow and flame characteristics. The emission of NOx is also similar to prototype by using Da<sc>i</sc> law. But Re law could keep flow characteristics under non-combustion state. It is suggested that Dai law is suitable for lean premixed swirl combustor geometry scaling.
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Ainslie, B., and D. G. Steyn. "A scaling analysis of ozone photochemistry: I Model development." Atmospheric Chemistry and Physics Discussions 5, no. 6 (December 19, 2005): 12957–83. http://dx.doi.org/10.5194/acpd-5-12957-2005.
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Abstract. A scaling analysis has been used to capture the integrated behaviour of several photochemical mechanisms for a wide range of precursor concentrations and a variety of environmental conditions. The Buckingham Pi method of dimensional analysis was used to express the relevant variables in terms of dimensionless groups. These grouping show maximum ozone, initial NOx and initial VOC concentrations are made non-dimensional by the average NO2 photolysis rate (jav) and the rate constant for the NO-O3 titration reaction (kNO); temperature by the NO-O3 activation energy (ENO) and Boltzmann constant (k) and total irradiation time by the cumulative javΔt photolysis rate (π3). The analysis shows dimensionless maximum ozone concentration can be described by a product of powers of dimensionless initial NOx concentration, dimensionless temperature, and a similarity curve directly dependent on the ratio of initial VOC to NOx concentration and implicitly dependent on the cumulative NO2 photolysis rate. When Weibull transformed, the similarity relationship shows a scaling break with dimensionless model output clustering onto two straight line segments, parameterized using four variables: two describing the slopes of the line segments and two giving the location of their intersection. A fifth parameter is used to normalize the model output. The scaling analysis, similarity curve and parameterization appear to be independent of the details of the chemical mechanism, hold for a variety of VOC species and mixtures and a wide range of temperatures and actinic fluxes.
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Tang, W., D. Cohan, L. N. Lamsal, X. Xiao, and W. Zhou. "Inverse modeling of Texas NO<sub>x</sub> emissions using space-based and ground-based NO<sub>2</sub> observations." Atmospheric Chemistry and Physics Discussions 13, no. 7 (July 2, 2013): 17479–517. http://dx.doi.org/10.5194/acpd-13-17479-2013.
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Abstract. Inverse modeling of nitrogen oxide (NOx) emissions using satellite-based NO2 observations has become more prevalent in recent years, but has rarely been applied to regulatory modeling at regional scales. In this study, OMI satellite observations of NO2 column densities are used to conduct inverse modeling of NOx emission inventories for two Texas State Implementation Plan (SIP) modeling episodes. Addition of lightning, aircraft, and soil NOx emissions to the regulatory inventory narrowed but did not close the gap between modeled and satellite observed NO2 over rural regions. Satellite-based top-down emission inventories are created with the regional Comprehensive Air Quality Model with extensions (CAMx) using two techniques: the direct scaling method and discrete Kalman filter (DKF) with Decoupled Direct Method (DDM) sensitivity analysis. The simulations with satellite-inverted inventories are compared to the modeling results using the a priori inventory as well as an inventory created by a ground-level NO2 based DKF inversion. The DKF inversions yield conflicting results: the satellite-based inversion scales up the a priori NOx emissions in most regions by factors of 1.02 to 1.84, leading to 3–55% increase in modeled NO2 column densities and 1–7 ppb increase in ground 8 h ozone concentrations, while the ground-based inversion indicates the a priori NOx emissions should be scaled by factors of 0.34 to 0.57 in each region. However, none of the inversions improve the model performance in simulating aircraft-observed NO2 or ground-level ozone (O3) concentrations.
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Tang, W., D. S. Cohan, L. N. Lamsal, X. Xiao, and W. Zhou. "Inverse modeling of Texas NO<sub>x</sub> emissions using space-based and ground-based NO<sub>2</sub> observations." Atmospheric Chemistry and Physics 13, no. 21 (November 12, 2013): 11005–18. http://dx.doi.org/10.5194/acp-13-11005-2013.
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Abstract. Inverse modeling of nitrogen oxide (NOx) emissions using satellite-based NO2 observations has become more prevalent in recent years, but has rarely been applied to regulatory modeling at regional scales. In this study, OMI satellite observations of NO2 column densities are used to conduct inverse modeling of NOx emission inventories for two Texas State Implementation Plan (SIP) modeling episodes. Addition of lightning, aircraft, and soil NOx emissions to the regulatory inventory narrowed but did not close the gap between modeled and satellite-observed NO2 over rural regions. Satellite-based top-down emission inventories are created with the regional Comprehensive Air Quality Model with extensions (CAMx) using two techniques: the direct scaling method and discrete Kalman filter (DKF) with decoupled direct method (DDM) sensitivity analysis. The simulations with satellite-inverted inventories are compared to the modeling results using the a priori inventory as well as an inventory created by a ground-level NO2-based DKF inversion. The DKF inversions yield conflicting results: the satellite-based inversion scales up the a priori NOx emissions in most regions by factors of 1.02 to 1.84, leading to 3–55% increase in modeled NO2 column densities and 1–7 ppb increase in ground 8 h ozone concentrations, while the ground-based inversion indicates the a priori NOx emissions should be scaled by factors of 0.34 to 0.57 in each region. However, none of the inversions improve the model performance in simulating aircraft-observed NO2 or ground-level ozone (O3) concentrations.
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Edland, Rikard, Fredrik Normann, Thomas Allgurén, Christian Fredriksson, and Klas Andersson. "Scaling of Pulverized-Fuel Jet Flames That Apply Large Amounts of Excess Air—Implications for NOx Formation." Energies 12, no. 14 (July 12, 2019): 2680. http://dx.doi.org/10.3390/en12142680.
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Measures to reduce nitrogen oxides (NOx) formation in industrial combustion processes often require up-scaling through pilot-scale facilities prior to being implemented in commercial scale, and scaling is therefore an important aspect of achieving lower NOx emissions. The current paper is a combined experimental and modelling study that aims to expand the understanding of constant velocity scaling for industrial jet flames applying high amounts of excess air. These types of flames are found in e.g., rotary kilns for production of iron ore pellets. The results show that, even if the combustion settings, velocity, and temperature profiles are correctly scaled, the concentration of oxygen experienced by the fuel during char combustion will scale differently. As the NO formation from the char combustion is important in these flames, the differences induced by the scaling has important impacts on the efficiencies of the applied primary measures. Increasing the rate of char combustion (to increase the Damköhler number), by using, for example, smaller-sized particles, in the pilot-scale is recommended to improve scaling.
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Ensberg, J. J., M. Carreras-Sospedra, and D. Dabdub. "Impacts of electronically photo-excited NO<sub>2</sub> on air pollution control strategies in the South Coast Air Basin of California." Atmospheric Chemistry and Physics Discussions 9, no. 5 (September 11, 2009): 18985–9008. http://dx.doi.org/10.5194/acpd-9-18985-2009.
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Abstract. A new path for hydroxyl radical formation via photo-excitation of nitrogen dioxide (NO2) and the reaction of photo-excited NO2 with water is evaluated using the UCI-CIT model for the South Coast Air Basin of California (SoCAB). Two separate studies predict different reaction rates, which differ by nearly an order of magnitude, for the reaction of photo-excited NO2 with water. Impacts of this new chemical mechanism on ozone and particulate matter formation, while utilizing both reaction rates, are quantified by simulating a two-day summer episode. In addition, sensitivity simulations are conducted to evaluate the uncertainty in the rate of reaction of photo-excited NO2 with water reported in the literature. Results indicate that the addition of photo-excited NO2 chemistry increases peak 1-h average ozone concentrations by up to 20.6%. Also, the new chemistry leads to moderate increases in particulate matter concentrations of up to 2.9%. The importance of this new chemistry is then evaluated in the context of pollution control strategies. A series of simulations are conducted to generate isopleths for ozone and particulate matter concentrations, varying baseline nitrogen oxides (NOx) and volatile organic compounds emissions. Results show that including NO2 photo-excitation increases the sensitivity of ozone concentration to changes in NOx emissions. Namely, increasing NOx when NO2 photo-excitation is included, while utilizing the higher reaction rate, leads to an increase in ozone concentration of up to 38.7% higher than a case without photo-excited NO2. Ozone and particulate matter control strategies rely heavily on the variation of NOx and VOC emissions and the addition of the new chemical mechanism increases peak ozone and 24-h average PM concentrations in all locations under all NOx and VOC scaling factors while utilizing both reaction rates. Therefore, three-dimensional air quality models should be modified to include this new OH production mechanism, especially if used to develop emission controls strategies.
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Hwang, Jeongjae, Kitae Sohn, Nicolas Bouvet, and Youngbin Yoon. "NOx Scaling of Syngas H2/CO Turbulent Non-Premixed Jet Flames." Combustion Science and Technology 185, no. 12 (December 2, 2013): 1715–34. http://dx.doi.org/10.1080/00102202.2013.831847.
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SZEGO, G., B. DALLY, and G. NATHAN. "Scaling of NOx emissions from a laboratory-scale mild combustion furnace." Combustion and Flame 154, no. 1-2 (July 2008): 281–95. http://dx.doi.org/10.1016/j.combustflame.2008.02.001.
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Simon, Heather, Barron H. Henderson, R. Chris Owen, Kristen M. Foley, Michelle G. Snyder, and Sue Kimbrough. "Variability in Observation-Based Onroad Emission Constraints from a Near-Road Environment." Atmosphere 11, no. 11 (November 18, 2020): 1243. http://dx.doi.org/10.3390/atmos11111243.
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This study uses Las Vegas near-road measurements of carbon monoxide (CO) and nitrogen oxides (NOx) to test the consistency of onroad emission constraint methodologies. We derive commonly used CO to NOx ratios (∆CO:∆NOx) from cross-road gradients and from linear regression using ordinary least squares (OLS) regression and orthogonal regression. The CO to NOx ratios are used to infer NOx emission adjustments for a priori emissions estimates from EPA’s MOtor Vehicle Emissions Simulator (MOVES) model assuming unbiased CO. The assumption of unbiased CO emissions may not be appropriate in many circumstances but was implemented in this analysis to illustrate the range of NOx scaling factors that can be inferred based on choice of methods and monitor distance alone. For the nearest road estimates (25 m), the cross-road gradient and ordinary least squares (OLS) agree with each other and are not statistically different from the MOVES-based emission estimate while ∆CO:∆NOx from orthogonal regression is significantly higher than the emitted ratio from MOVES. Using further downwind measurements (i.e., 115 m and 300 m) increases OLS and orthogonal regression estimates of ∆CO:∆NOx but not cross-road gradient ∆CO:∆NOx. The inferred NOx emissions depend on the observation-based method, as well as the distance of the measurements from the roadway and can suggest either that MOVES NOx emissions are unbiased or that they should be adjusted downward by between 10% and 47%. The sensitivity of observation-based ∆CO:∆NOx estimates to the selected monitor location and to the calculation method characterize the inherent uncertainty of these methods that cannot be derived from traditional standard-error based uncertainty metrics.
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Baumgaertner, A. J. G., P. Jöckel, and C. Brühl. "Energetic particle precipitation in ECHAM5/MESSy1 – Part 1: Downward transport of upper atmospheric NO<sub>x</sub> produced by low energy electrons." Atmospheric Chemistry and Physics Discussions 8, no. 6 (December 18, 2008): 21201–28. http://dx.doi.org/10.5194/acpd-8-21201-2008.
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Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy1 has been extended by processes that parameterize particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In the companion paper, the ECHAM5/MESSy1 solar proton event parameterization is discussed, while in the current paper we focus on low energy electrons (LEE) that produce NOx in the upper atmosphere. For the flux of LEE NOx into the top of the model domain a novel technique which can be applied to most atmospheric chemistry general circulation models has been developed and is presented here. The technique is particularly useful for models with an upper boundary between the stratopause and mesopause and therefore cannot directly incorporate upper atmospheric NOx production. The additional NOx source parametrization is based on a measure of geomagnetic activity, the Ap index, which has been shown to be a good proxy for LEE NOx interannual variations. HALOE measurements of LEE NOx that has been transported into the stratosphere are used to develop a scaling function which yields a flux of NOx that is applied to the model top. We describe the implementation of the parameterization as the submodel SPACENOX in ECHAM5/MESSy1 and discuss the results from test simulations. The NOx enhancements and associated effects on ozone are shown to be in good agreement with independent measurements. Ap index data is available for almost one century, thus the parameterization is suitable for simulations of the recent climate.
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Baumgaertner, A. J. G., P. Jöckel, and C. Brühl. "Energetic particle precipitation in ECHAM5/MESSy1 – Part 1: Downward transport of upper atmospheric NO<sub>x</sub> produced by low energy electrons." Atmospheric Chemistry and Physics 9, no. 8 (April 24, 2009): 2729–40. http://dx.doi.org/10.5194/acp-9-2729-2009.
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Abstract. The atmospheric chemistry general circulation model ECHAM5/MESSy1 has been extended by processes that parameterise particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In the companion paper, the ECHAM5/MESSy1 solar proton event parametrisation is discussed, while in the current paper we focus on low energy electrons (LEE) that produce NOx in the upper atmosphere. For the flux of LEE NOx into the top of the model domain a novel technique which can be applied to most atmospheric chemistry general circulation models has been developed and is presented here. The technique is particularly useful for models with an upper boundary between the stratopause and mesopause and therefore cannot directly incorporate upper atmospheric NOx production. The additional NOx source parametrisation is based on a measure of geomagnetic activity, the Ap index, which has been shown to be a good proxy for LEE NOx interannual variations. HALOE measurements of LEE NOx that has been transported into the stratosphere are used to develop a scaling function which yields a flux of NOx that is applied to the model top. We describe the implementation of the parametrisation as the submodel SPACENOX in ECHAM5/MESSy1 and discuss the results from test simulations. The NOx enhancements are shown to be in good agreement with independent measurements. Ap index data is available for almost one century, thus the parametrisation is suitable for simulations of the recent climate.
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Ghadiri, H., J. Hussein, and C. W. Rose. "Effect of pasture buffer length and pasture type on runoff water quality following prescribed burning in the Wivenhoe Catchment." Soil Research 49, no. 6 (2011): 513. http://dx.doi.org/10.1071/sr11122.
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Burning of pastures is a management practice adopted by graziers worldwide. When rain falls on burnt pastures, it can lead to increased pollutant transport in runoff. However, this transport can be modified by vegetative buffers which intercept the runoff downslope of burnt areas. This study examines the effects of different pasture buffer lengths (0, 2, and 5 m) on sediment and chemical transport from two pasture sites near Wivenhoe Dam, the main water reservoir for Brisbane City. Simulated rainfall (100 mm/h) was applied to 18 plots on pasture sites after they were burnt, and insoluble and soluble components were measured in the runoff. Most eroded sediment/organic debris accumulated against the first row of the grass buffer strips or was deposited in the upslope backwater region. Buffer length had little impact on the runoff concentrations of NO3– and NO2– (NOx), total Kjeldahl nitrogen, and total nitrogen from the 5-m-length upslope plots but was significant for sediment loss rate, filterable reactive phosphate, ammonium, and total and dissolved organic carbon. Pasture type was significant for NOx, ammonium, sediment loss rate, and total organic carbon only. Burning increased enrichment ratios of nutrients and carbon in the runoff compared with unburnt plots, but a 2-m buffer strip subsequently reduced the enrichment ratio values by >30%. Buffers strips of unburnt pasture grass may provide an effective tool for post-fire erosion control following prescribed burning; however, further work including scaling to larger plot sizes and catchment level is required.
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Tagaris, E., R. E. P. Sotiropoulou, N. Gounaris, S. Andronopoulos, and D. Vlachogiannis. "Air quality over Europe: modeling gaseous and particulate pollutants and the effect of precursor emissions." Atmospheric Chemistry and Physics Discussions 13, no. 3 (March 13, 2013): 6681–705. http://dx.doi.org/10.5194/acpd-13-6681-2013.
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Abstract. Air quality over Europe using Models-3 (i.e. CMAQ, MM5, SMOKE) modeling system is performed for winter (i.e. January, 2006) and summer (i.e. July, 2006) months with the 2006 TNO gridded anthropogenic emissions database. Higher ozone concentrations are illustrated in southern Europe while higher NO2 concentrations are simulated over western Europe. Elevated SO2 concentrations are simulated over eastern Europe while elevated PM2.5 levels are simulated over eastern and western Europe. Results suggest that NO2 and PM2.5 are underpredicted, SO2 is overpredicted while Max8hrO3 is overpredicted for low concentrations and is underpredicted for the higher ones. Speciated PM2.5 components suggest that NO3 is dominant during winter in western Europe and in a few eastern countries due to the high NO2 concentrations. During summer NO3 is dominant only in regions with elevated NH3 emissions. For the rest of the domain SO4 is dominant. Low OC concentrations are simulated mainly due to the uncertain representation of SOA formation. The difference between observed and predicted concentrations for each country is assessed for the gaseous and particulate pollutants. The simultaneous precursor emissions change applying scaling factors on NOx, SO2 and PM2.5 emissions based on the observed/predicted ratio for each country seems to statistically enhance model performance (in gaseous pollutants the improvement in root mean square is up to 5.6 ppbV, in the index of agreement is up to 0.3 and in the mean absolute error is up to 4.2 ppbV while the related values in PM2.5 are 4.5 μg m−3, 0.2 and 3.5 μg m−3, respectively).
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Hsu, H. m., C. Y. Lin, A. Guenther, J. J. Tribbia, and S. C. Liu. "Air-chemistry "turbulence": power-law scaling and statistical regularity." Atmospheric Chemistry and Physics Discussions 11, no. 3 (March 22, 2011): 9635–72. http://dx.doi.org/10.5194/acpd-11-9635-2011.
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Abstract. With the intent to gain further knowledge on the spectral structures and statistical regularities of surface atmospheric chemistry, the chemical gases (NO, NO2, NOx, CO, SO2, and O3) and aerosol (PM10) measured at 74 air quality monitoring stations over the island of Taiwan are analyzed for the year of 2004 at hourly resolution. They represent a range of surface air quality with a mixed combination of geographic settings, and include urban/rural, coastal/inland, and plain/hill locations. In addition to the well-known semi-diurnal and diurnal oscillations, weekly, intermediate (20 ~ 30 days) and intraseasonal (30 ~ 100 days) peaks are also identified with the continuous wavelet transform (CWT). The spectra indicate power-law scaling regions for the frequencies higher than the diurnal and those lower than the diurnal with the average exponents of −5/3 and −1, respectively. These dual-exponents are corroborated with those with the detrended fluctuation analysis in the corresponding time-lag regions. After spectral coefficients from the CWT decomposition are grouped according to the spectral bands, and inverted separately, the PDFs of the reconstructed time series for the high-frequency band demonstrate the interesting statistical regularity, −3 power-law scaling for the heavy tails, consistently. Such spectral peaks, dual-exponent structures, and power-law scaling in heavy tails are intriguingly interesting, but their relations to turbulence and mesoscale variability require further investigations. This could lead to a better understanding of the processes controlling air quality.
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Santos, A., and M. Costa. "Reexamination of the scaling laws for NOx emissions from hydrocarbon turbulent jet diffusion flames." Combustion and Flame 142, no. 1-2 (July 2005): 160–69. http://dx.doi.org/10.1016/j.combustflame.2005.03.004.
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Tost, H., P. Jöckel, and J. Lelieveld. "Lightning and convection parameterisations – uncertainties in global modelling." Atmospheric Chemistry and Physics Discussions 7, no. 3 (May 21, 2007): 6767–801. http://dx.doi.org/10.5194/acpd-7-6767-2007.
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Abstract. The simulation of convection, lightning and subsequent NOx emissions with global atmospheric chemistry models is associated with large uncertainties since these processes are heavily parameterised. Each parameterisation by itself has deficiencies while the combination substantially increases the uncertainties from the individual parameterisations. In this study several combinations of state-of-the-art convection and lightning parameterisations are used in model simulations with the global atmospheric chemistry model ECHAM5/MESSy and are evaluated against lightning observations. A wide range in the spatial and temporal variability of the simulated flash densities is found, attributed to both types of parameterisations. Some combinations perform well, whereas others are hardly applicable. In addition to resolution dependent rescaling parameters, each combination of lightning and convection schemes requires individual scaling to reproduce the observed flash frequencies. The resulting NOx profiles are inter-compared, but definite conclusions about the most realistic profiles can currently not be provided.
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Chuahy, Flavio DF, Jamen Olk, Dan DelVescovo, and Sage L. Kokjohn. "An engine size–scaling method for kinetically controlled combustion strategies." International Journal of Engine Research 21, no. 6 (July 15, 2018): 927–47. http://dx.doi.org/10.1177/1468087418786130.
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A substantial amount of research has recently focused on kinetically controlled combustion strategies such as reactivity-controlled compression ignition combustion. These strategies are promising methods to achieve high efficiency with near-zero NOx and soot emissions; however, despite promising results, very few attempts have been made to develop size-scaling relationships that would allow these results to be generalized to any engine design. Engine design is a long and arduous process that requires a substantial amount of experimental work. Consequently, it is of interest to develop scaling laws that allow results from one engine to be extrapolated to new designs. Several scaling laws have been proposed for diffusion combustion (i.e. mixing limited) that scale parameters such as liquid length and lift-off length. Such parameters have been deemed unimportant for highly premixed low-temperature combustion strategies; thus, a new methodology is needed. The present effort uses a combination of detailed computational fluid dynamics simulations and engine experiments in two engines with different bore sizes to develop a new engine size–scaling methodology for low-temperature kinetically controlled combustion strategies. The effects of pressure, temperature, and turbulence timescales are explored in order to replicate the large-bore engine performance in a small-bore engine. A size-scaling relationship based on the ignition timescale is proposed and used to generalize the results to an arbitrary bore size and fuel combination.
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Hsu, H. m., C. Y. Lin, A. Guenther, J. J. Tribbia, and S. C. Liu. "Air-chemistry "turbulence": power-law scaling and statistical regularity." Atmospheric Chemistry and Physics 11, no. 16 (August 18, 2011): 8395–413. http://dx.doi.org/10.5194/acp-11-8395-2011.
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Abstract. With the intent to gain further knowledge on the spectral structures and statistical regularities of surface atmospheric chemistry, the chemical gases (NO, NO2, NOx, CO, SO2, and O3) and aerosol (PM10) measured at 74 air quality monitoring stations over the island of Taiwan are analyzed for the year of 2004 at hourly resolution. They represent a range of surface air quality with a mixed combination of geographic settings, and include urban/rural, coastal/inland, plain/hill, and industrial/agricultural locations. In addition to the well-known semi-diurnal and diurnal oscillations, weekly, and intermediate (20 ~ 30 days) peaks are also identified with the continuous wavelet transform (CWT). The spectra indicate power-law scaling regions for the frequencies higher than the diurnal and those lower than the diurnal with the average exponents of −5/3 and −1, respectively. These dual-exponents are corroborated with those with the detrended fluctuation analysis in the corresponding time-lag regions. These exponents are mostly independent of the averages and standard deviations of time series measured at various geographic settings, i.e., the spatial inhomogeneities. In other words, they possess dominant universal structures. After spectral coefficients from the CWT decomposition are grouped according to the spectral bands, and inverted separately, the PDFs of the reconstructed time series for the high-frequency band demonstrate the interesting statistical regularity, −3 power-law scaling for the heavy tails, consistently. Such spectral peaks, dual-exponent structures, and power-law scaling in heavy tails are important structural information, but their relations to turbulence and mesoscale variability require further investigations. This could lead to a better understanding of the processes controlling air quality.
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Tost, H., P. Jöckel, and J. Lelieveld. "Lightning and convection parameterisations – uncertainties in global modelling." Atmospheric Chemistry and Physics 7, no. 17 (September 5, 2007): 4553–68. http://dx.doi.org/10.5194/acp-7-4553-2007.
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Abstract. The simulation of convection, lightning and consequent NOx emissions with global atmospheric chemistry models is associated with large uncertainties since these processes are heavily parameterised. Each parameterisation by itself has deficiencies and the combination of these substantially increases the uncertainties compared to the individual parameterisations. In this study several combinations of state-of-the-art convection and lightning parameterisations are used in simulations with the global atmospheric chemistry general circulation model ECHAM5/MESSy, and are evaluated against lightning observations. A wide range in the spatial and temporal variability of the simulated flash densities is found, attributed to both types of parameterisations. Some combinations perform well, whereas others are hardly applicable. In addition to resolution dependent rescaling parameters, each combination of lightning and convection schemes requires individual scaling to reproduce the observed flash frequencies. The resulting NOx profiles are inter-compared, however definite conclusions about the most realistic profiles can currently not be drawn.
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Sauvage, B., R. V. Martin, A. van Donkelaar, X. Liu, K. Chance, L. Jaeglé, P. I. Palmer, S. Wu, and T. M. Fu. "Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone." Atmospheric Chemistry and Physics 7, no. 3 (February 14, 2007): 815–38. http://dx.doi.org/10.5194/acp-7-815-2007.
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Abstract. We use a global chemical transport model (GEOS-Chem) to evaluate the consistency of satellite measurements of lightning flashes and ozone precursors with in situ measurements of tropical tropospheric ozone. The measurements are tropospheric O3, NO2, and HCHO columns from the GOME satellite instrument, lightning flashes from the OTD and LIS satellite instruments, profiles of O3, CO, and relative humidity from the MOZAIC aircraft program, and profiles of O3 from the SHADOZ ozonesonde network. We interpret these multiple data sources with our model to better understand what controls tropical tropospheric ozone. Tropical tropospheric ozone is mainly affected by lightning NOx and convection in the upper troposphere and by surface emissions in the lower troposphere. Scaling the spatial distribution of lightning in the model to the observed flashes improves the simulation of O3 in the upper troposphere by 5–20 ppbv versus in situ observations and by 1–4 Dobson Units versus GOME retrievals of tropospheric O3 columns. A lightning source strength of 6±2 Tg N/yr best represents in situ observations from aircraft and ozonesonde. Tropospheric NO2 and HCHO columns from GOME are applied to provide top-down constraints on emission inventories of NOx (biomass burning and soils) and VOCs (biomass burning). The top-down biomass burning inventory is larger than the bottom-up inventory by a factor of 2 for HCHO and alkenes, and by a factor of 2.6 for NOx over northern equatorial Africa. These emissions increase lower tropospheric O3 by 5–20 ppbv, improving the simulation versus aircraft observations, and by 4 Dobson Units versus GOME observations of tropospheric O3 columns. Emission factors in the a posteriori inventory are more consistent with a recent compilation from in situ measurements. The ozone simulation using two different dynamical schemes (GEOS-3 and GEOS-4) is evaluated versus observations; GEOS-4 better represents O3 observations by 5–15 ppbv, reflecting enhanced convective detrainment in the upper troposphere. Heterogeneous uptake of HNO3 on aerosols reduces simulated O3 by 5–7 ppbv, reducing a model bias versus in situ observations over and downwind of deserts. Exclusion of HO2 uptake on aerosols increases O3 by 5 ppbv in biomass burning regions, reducing a model bias versus MOZAIC aircraft measurements.
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Johansson, Jakob, Anette Heijnesson Hultén, Fredrik Normann, and Klas Andersson. "Simultaneous Removal of NOx and SOx from Flue Gases Using ClO2: Process Scaling and Modeling Simulations." Industrial & Engineering Chemistry Research 60, no. 4 (January 20, 2021): 1774–83. http://dx.doi.org/10.1021/acs.iecr.0c05828.
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Hsieh, T. C. Adrian, Werner J. A. Dahm, and James F. Driscoll. "Scaling Laws for NOx Emission Performance of Burners and Furnaces from 30 kW to 12 MW." Combustion and Flame 114, no. 1-2 (July 1998): 54–80. http://dx.doi.org/10.1016/s0010-2180(97)00289-7.
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Lanfredi, M., M. Macchiato, M. Ragosta, and C. Serio. "Time Correlation Structure in Hourly Concentration Time Series of CO, NOx and O3 in Urban Areas." Fractals 06, no. 02 (June 1998): 151–58. http://dx.doi.org/10.1142/s0218348x98000195.
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The timescales which govern urban pollution processes are investigated by analyzing variance spectra and structure functions of observational time series. The range of analyzed scales stretches from one hour to several days. It is shown that characteristic fluctuations of CO, NOx (primary pollutants) and O3 (secondary pollutant) follow a scale invariant law up to timescales of about one day. Scaling exponents indicate the presence of stabilizing feedback mechanisms. Such a scale invariance is broken by the appearance of basic periods which, for primary pollutants, are expressions of traffic dynamics, whereas, for ozone, are closely linked to the diurnal and annual solar cycles.
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Ancellet, G., E. Orlandi, E. Real, K. S. Law, H. Schlager, F. Fierli, V. Thouret, C. Mari, and J. Leclair de Bellevue. "Tropospheric ozone production related to West African city emissions during the 2006 wet season AMMA campaign." Atmospheric Chemistry and Physics Discussions 10, no. 11 (November 10, 2010): 27135–84. http://dx.doi.org/10.5194/acpd-10-27135-2010.
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Abstract. During the African Monsoon Multidisciplinary Analyses (AMMA) airborne measurements of ozone, CO and nitrogen oxides by the French and German falcon aircraft took place near three cities in West Africa (Cotonou, Niamey and Ouagadougou). Significant ozone production (O3 increase of 40–50 ppbv) took place during two specific events: one near Cotonou on the coast of the Guinea Gulf, and the other near Niamey in the Sahel region. In both cases a high level of NOx (>3 ppbv) is related to the ozone production. The ozone production is mainly driven by the Lagos-Cotonou anthropogenic emissions in Cotonou. In Niamey the combined effect of advection of VOC emissions from the forest and stagnation over the city area and the poorly vegetated soils recently wetted by convected systems is needed to achieve a similar level of ozone precursors. In Ouagadougou no ozone plume is found because of the absence of a pause in the convective activity and of the larger vegetated area around the city which prevented ozone plume formation during the wet season. To discuss the ozone increase near Cotonou two different approaches have been implemented: a FLEXPART simulation to quantify the probability of transport from the SH compared to air mass stagnation over the emission area and a simulation of the BOLAM mesoscale model with two different tracers for the anthropogenic emission (RETRO inventory for 2000) and the biomass burning. The BOLAM model shows a good agreement with the meteorological observations of the aircraft and allows to identify the key influence of the anthropogenic emissions in the first 3 km while the biomass burning plume remains above this altitude. The day to day variability of the ozone and CO in Niamey and Ouagadougou is discussed using FLEXPART simulations of the air mass stagnation in the 12° N–14° N latitude band and northward advection of air masses from the vegetated areas influenced by the biogenic volatile organic compound (VOC) emissions. Both conditions need to be fulfilled to be able to detect ozone increase within the city plume. The first condition is necessary to obtain a significant increase of the NOx concentrations by combining the city emission and the soil emission. It also shows that, contrary to the Niamey conditions, the Ouagadougou air mass transport and its timing respective to the convective activity did not correspond to favourable conditions for O3 formation during the time period of the aircraft data. Finally to check the magnitude of the ozone production related to the observed CO and NOx observations, a 2-days stationary run of the CittyCAT Lagrangian model was conducted at Cotonou location. The initialisation of the chemical concentrations not measured is done by scaling to the NOx and CO concentrations observed in the polluted plume. The scaling factor is derived from the low altitude observations provided by the DF20 and the BAe-146 aircraft during the AMMA campaign. Under such conditions, the simulation show that 50 ppbv of ozone can be produced in a 2-days period.
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Parrington, M., P. I. Palmer, D. K. Henze, D. W. Tarasick, E. J. Hyer, R. C. Owen, D. Helmig, et al. "The influence of boreal biomass burning emissions on the distribution of tropospheric ozone over North America and the North Atlantic during 2010." Atmospheric Chemistry and Physics Discussions 11, no. 9 (September 8, 2011): 25099–153. http://dx.doi.org/10.5194/acpd-11-25099-2011.
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Abstract. We analyse the tropospheric ozone distribution over North America and the North Atlantic to boreal biomass burning emissions during the summer of 2010 using the GEOS-Chem 3-D global tropospheric chemical transport model, and observations from in situ and satellite instruments. In comparison to observations from the PICO-NARE observatory in the Azores, ozonesondes across Canada, and the Tropospheric Emission Spectrometer (TES) and Infrared Atmospheric Sounding Instrument (IASI) satellite instruments, the model ozone distribution is shown to be in reasonable agreement with mean biases less than 10 ppbv. We use the adjoint of GEOS-Chem to show the model ozone distribution in the free troposphere over Maritime Canada is largely sensitive to NOx emissions from biomass burning sources in Central Canada, lightning sources in the central US, and anthropogenic sources in eastern US and south-eastern Canada. We also use the adjoint of GEOS-Chem to evaluate the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory through assimilation of CO observations from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument. The CO inversion showed that, on average the FLAMBE emissions needed to be reduced to 89 % of their original values, with scaling factors ranging from 12 % to 102 %, to fit the MOPITT observations in the boreal regions. Applying the CO scaling factors to all species emitted from boreal biomass burning sources led to a decrease of the model tropospheric distributions of CO, PAN, and NOx by as much as −20 ppbv, −50 ppbv, and −20 ppbv respectively. The impact of optimizing the biomass burning emissions was to reduce the model ozone distribution by approximately −3 ppbv (−8 %) and on average improved the agreement of the model ozone distribution compared to the observations throughout the free troposphere reducing the mean model bias from 5.5 to 4.0 ppbv for the PICO-NARE observatory, 3.0 to 0.9 ppbv for ozonesondes, 2.0 to 0.9 ppbv for TES, and 2.8 to 1.4 ppbv for IASI.
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Parrington, M., P. I. Palmer, D. K. Henze, D. W. Tarasick, E. J. Hyer, R. C. Owen, D. Helmig, et al. "The influence of boreal biomass burning emissions on the distribution of tropospheric ozone over North America and the North Atlantic during 2010." Atmospheric Chemistry and Physics 12, no. 4 (February 21, 2012): 2077–98. http://dx.doi.org/10.5194/acp-12-2077-2012.
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Abstract. We have analysed the sensitivity of the tropospheric ozone distribution over North America and the North Atlantic to boreal biomass burning emissions during the summer of 2010 using the GEOS-Chem 3-D global tropospheric chemical transport model and observations from in situ and satellite instruments. We show that the model ozone distribution is consistent with observations from the Pico Mountain Observatory in the Azores, ozonesondes across Canada, and the Tropospheric Emission Spectrometer (TES) and Infrared Atmospheric Sounding Instrument (IASI) satellite instruments. Mean biases between the model and observed ozone mixing ratio in the free troposphere were less than 10 ppbv. We used the adjoint of GEOS-Chem to show the model ozone distribution in the free troposphere over Maritime Canada is largely sensitive to NOx emissions from biomass burning sources in Central Canada, lightning sources in the central US, and anthropogenic sources in the eastern US and south-eastern Canada. We also used the adjoint of GEOS-Chem to evaluate the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory through assimilation of CO observations from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument. The CO inversion showed that, on average, the FLAMBE emissions needed to be reduced to 89% of their original values, with scaling factors ranging from 12% to 102%, to fit the MOPITT observations in the boreal regions. Applying the CO scaling factors to all species emitted from boreal biomass burning sources led to a decrease of the model tropospheric distributions of CO, PAN, and NOx by as much as −20 ppbv, −50 pptv, and −20 pptv respectively. The modification of the biomass burning emission estimates reduced the model ozone distribution by approximately −3 ppbv (−8%) and on average improved the agreement of the model ozone distribution compared to the observations throughout the free troposphere, reducing the mean model bias from 5.5 to 4.0 ppbv for the Pico Mountain Observatory, 3.0 to 0.9 ppbv for ozonesondes, 2.0 to 0.9 ppbv for TES, and 2.8 to 1.4 ppbv for IASI.
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Huszar, P., H. Teyssèdre, M. Michou, A. Voldoire, D. J. L. Olivié, D. Saint-Martin, D. Cariolle, et al. "Modeling the present and future impact of aviation on climate: an AOGCM approach with online coupled chemistry." Atmospheric Chemistry and Physics 13, no. 19 (October 11, 2013): 10027–48. http://dx.doi.org/10.5194/acp-13-10027-2013.
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Abstract. Our work is among the first that use an atmosphere-ocean general circulation model (AOGCM) with online chemistry to evaluate the impact of future aviation emissions on temperature. Other particularities of our study include non-scaling to the aviation emissions, and the analysis of models' transient response using ensemble simulations. The model we use is the Météo-France CNRM-CM5.1 earth system model extended with the REPROBUS chemistry scheme. The time horizon of our interest is 1940–2100, assuming the A1B SRES scenario. We investigate the present and future impact of aviation emissions of CO2, NOx and H2O on climate, taking into account changes in greenhouse gases, contrails and contrail-induced cirrus (CIC). As in many transport-related impact studies, we distinguish between the climate impacts of CO2 emissions and those of non-CO2 emissions. Aviation-produced aerosol is not considered in the study. Our modeling system simulated a notable sea-ice bias in the Arctic, and therefore results concerning the surface should be viewed with caution. The global averaged near-surface CO2 impact reaches around 0.1 K by the end of the 21st century, while the non-CO2 impact reaches 0.2 K in the second half of the century. The NOx emissions impact is almost negligible in our simulations, as our aviation-induced ozone production is small. As a consequence, the non-CO2 signal is very similar to the CIC signal. The seasonal analysis shows that the strongest warming due to aviation is modeled for the late summer and early autumn. In the stratosphere, a significant cooling is attributed to aviation CO2 emissions (−0.25 K by 2100). A −0.3 K temperature decrease is modeled when considering all the aviation emissions, but no significant signal appears from the CIC or NOx forcings in the stratosphere.
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Sauvage, B., R. V. Martin, A. van Donkelaar, X. Liu, K. Chance, L. Jaeglé, P. I. Palmer, S. Wu, and T. M. Fu. "Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone." Atmospheric Chemistry and Physics Discussions 6, no. 6 (November 17, 2006): 11465–520. http://dx.doi.org/10.5194/acpd-6-11465-2006.
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Abstract. We use a global chemical transport model (GEOS-Chem) to evaluate the consistency of satellite measurements of lightning flashes and ozone precursors with in situ measurements of tropical tropospheric ozone. The measurements are tropospheric O3, NO2, and HCHO columns from the GOME satellite instrument, lightning flashes from the OTD and LIS instruments, profiles of O3, CO, and relative humidity from the MOZAIC aircraft program, and profiles of O3 from the SHADOZ ozonesonde network. We interpret these multiple data sources with our model to better understand what controls tropical tropospheric ozone. Tropical tropospheric ozone is mainly affected by lightning and convection in the upper troposphere and by surface emissions in the lower troposphere. Scaling the spatial distribution of lightning in the model to the observed flash counts improves the simulation of O3 in the upper troposphere by 5–20 ppbv versus in situ observations and by 1–4 Dobson Units versus GOME retrievals of tropospheric O3 columns. A lightning source strength of 5±2 Tg N/yr best represents in situ observations from aircraft and ozonesonde. Tropospheric NO2 and HCHO columns from GOME are applied to provide top-down constraints on emission inventories of NOx (biomass burning and soils) and VOCs (biomass burning). The top-down biomass burning inventory is larger by a factor of 2 for HCHO and alkenes, and by 2.6 for NOx over northern equatorial Africa. These emissions increase lower tropospheric O3 by 5–20 ppbv, improving the simulation versus aircraft observations, and by 4 Dobson Units versus GOME observations of tropospheric O3 columns. Emission factors in the a posteriori inventory are more consistent with a recent compilation from in situ measurements. The ozone simulation using two different dynamical schemes (GEOS-3 and GEOS-4) is evaluated versus observations; GEOS-4 better represents O3 observations by 5–15 ppbv due to enhanced convective detrainment in the upper troposphere. Heterogeneous uptake of HNO3 on aerosols reduces simulated O3 by 5–7 ppbv, reducing a model bias versus in situ observations over and downwind of deserts. Exclusion of HO2 uptake on aerosols improves O3 by 5 ppbv in biomass burning regions.
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Thorp, Thomas, Stephen R. Arnold, Richard J. Pope, Dominick V. Spracklen, Luke Conibear, Christoph Knote, Mikhail Arshinov, et al. "Late-spring and summertime tropospheric ozone and NO<sub>2</sub> in western Siberia and the Russian Arctic: regional model evaluation and sensitivities." Atmospheric Chemistry and Physics 21, no. 6 (March 25, 2021): 4677–97. http://dx.doi.org/10.5194/acp-21-4677-2021.
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Abstract. We use a regional chemistry transport model (Weather Research and Forecasting model coupled with chemistry, WRF-Chem) in conjunction with surface observations of tropospheric ozone and Ozone Monitoring Instrument (OMI) satellite retrievals of tropospheric column NO2 to evaluate processes controlling the regional distribution of tropospheric ozone over western Siberia for late spring and summer in 2011. This region hosts a range of anthropogenic and natural ozone precursor sources, and it serves as a gateway for near-surface transport of Eurasian pollution to the Arctic. However, there is a severe lack of in situ observations to constrain tropospheric ozone sources and sinks in the region. We show widespread negative bias in WRF-Chem tropospheric column NO2 when compared to OMI satellite observations from May–August, which is reduced when using ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) v5a emissions (fractional mean bias (FMB) = −0.82 to −0.73) compared with the EDGAR (Emissions Database for Global Atmospheric Research)-HTAP (Hemispheric Transport of Air Pollution) v2.2 emissions data (FMB = −0.80 to −0.70). Despite the large negative bias, the spatial correlations between model and observed NO2 columns suggest that the spatial pattern of NOx sources in the region is well represented. Scaling transport and energy emissions in the ECLIPSE v5a inventory by a factor of 2 reduces column NO2 bias (FMB = −0.66 to −0.35), but with overestimates in some urban regions and little change to a persistent underestimate in background regions. Based on the scaled ECLIPSE v5a emissions, we assess the influence of the two dominant anthropogenic emission sectors (transport and energy) and vegetation fires on surface NOx and ozone over Siberia and the Russian Arctic. Our results suggest regional ozone is more sensitive to anthropogenic emissions, particularly from the transport sector, and the contribution from fire emissions maximises in June and is largely confined to latitudes south of 60∘ N. Ozone dry deposition fluxes from the model simulations show that the dominant ozone dry deposition sink in the region is to forest vegetation, averaging 8.0 Tg of ozone per month, peaking at 10.3 Tg of ozone deposition during June. The impact of fires on ozone dry deposition within the domain is small compared to anthropogenic emissions and is negligible north of 60∘ N. Overall, our results suggest that surface ozone in the region is controlled by an interplay between seasonality in atmospheric transport patterns, vegetation dry deposition, and a dominance of transport and energy sector emissions.
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Beekmann, M., A. Kerschbaumer, E. Reimer, R. Stern, and D. Möller. "PM measurement campaign HOVERT in the Greater Berlin area: model evaluation with chemically specified particulate matter observations for a one year period." Atmospheric Chemistry and Physics Discussions 6, no. 4 (August 2, 2006): 7285–321. http://dx.doi.org/10.5194/acpd-6-7285-2006.
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Abstract. The HOVERT (Horizontal and VERtical Transport of Ozone and particulate matter) campaign held in the Berlin Brandenburg area in Eastern Germany from September 2001 to September 2002 allowed to collect a unique data set of the aerosol chemical speciation (daily averages) at traffic, urban and rural sites. These observations are used for a thorough evaluation of the aerosol part in the REM-CALGRID model (RCG) developed at the Free University of Berlin (FUB). For inorganic ions (sulphate, nitrate and ammonium), simulated annual averages agree to observations within ±30% at more than half of the sites and always within a factor of two. Correlation coefficients are larger than in previous studies for SO42- and NH4+ (>0.7). For nitrate, less elevated correlations, 0.4–0.7 in the cold season, 0.2–0.4 in the warm season, are encountered. To our knowledge, this is one of the first comparisons of air quality model simulated elemental carbon (EC and OC) with daily observations for a whole year. It suggests an overestimation of EC and OC emissions in the Berlin area (through a scaling techniques between EC, OC and NOx and when assuming correct NOx emissions), and an underestimation of EC and OC at rural sites. Secondary organic aerosol (SOA) formation, recently introduced into the model (SORGAM module, Schell et al., 2001), is simulated as a very variable process, SOA levels varying from close to zero for most days to more than 5 µg/m3. Correlation between simulated SOA to observed OC is about 0.6, indicating that simulated variability partly corresponds to reality.
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Beekmann, M., A. Kerschbaumer, E. Reimer, R. Stern, and D. Möller. "PM measurement campaign HOVERT in the Greater Berlin area: model evaluation with chemically specified particulate matter observations for a one year period." Atmospheric Chemistry and Physics 7, no. 1 (January 10, 2007): 55–68. http://dx.doi.org/10.5194/acp-7-55-2007.
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Abstract. The HOVERT (HOrizontal and VERtical Transport of ozone and particulate matter) campaign held in the Berlin Brandenburg area in Eastern Germany from September 2001 to September 2002 allowed to collect a unique data set of the aerosol chemical speciation (daily averages) at traffic, urban and rural sites. These observations are used for a thorough evaluation of the aerosol part in the REM-CALGRID model (RCG) developed at the Free University of Berlin (FUB). For inorganic ions (sulphate, nitrate and ammonium), simulated annual averages agree to observations within ±30% at more than half of the sites and always within a factor of two. Correlation coefficients are larger than in previous studies for SO42− and NH4+ (>0.7). For nitrate, less elevated correlations, 0.4–0.7 in the cold season, 0.2–0.4 in the warm season, are encountered. To our knowledge, this is one of the first comparisons of air quality model simulated elemental and organic carbon (EC and OC) with daily observations for a whole year. It suggests an overestimation of EC and OC emissions in the Berlin area (through a scaling techniques between EC, OC and NOx and when assuming correct NOx emissions), and an underestimation of EC and OC at rural sites. Secondary organic aerosol (SOA) formation, recently introduced into the model (SORGAM module, Schell et al., 2001), is simulated as a very variable process, SOA levels varying from close to zero for most days to more than 5 μg/m3. Correlation between simulated SOA to observed OC is about 0.6, indicating that simulated variability partly corresponds to reality.
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Freitag, Lori, and Timothy Urness. "Analyzing Industrial Furnace Efficiency Using Comparative Visualization in a Virtual Reality Environment." Journal of Manufacturing Science and Engineering 124, no. 2 (April 29, 2002): 456–61. http://dx.doi.org/10.1115/1.1445150.
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We describe an interactive toolkit used to perform comparative analysis of two or more data sets arising from numerical simulations. Several techniques have been incorporated into this toolkit, including (1) successive visualization of individual data sets, (2) data comparison techniques such as computation and visualization of the differences between data sets, and (3) image comparison methods such as scalar field height profiles plotted in a common coordinate system. We describe each technique in detail and show example usage in an industrial application aimed at designing an efficient, low-NOx burner for industrial furnaces. Critical insights are obtained by interactively adjusted color maps, data culling, and data manipulation. New paradigms for scaling small values in the data comparison technique are described. The display device used for this application is the CAVE virtual reality theater, and we describe the user interface to the visualization toolkit and the benefits of immersive 3D visualization for comparative analysis.
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Vaughan, Adam R., James D. Lee, Pawel K. Misztal, Stefan Metzger, Marvin D. Shaw, Alastair C. Lewis, Ruth M. Purvis, et al. "Spatially resolved flux measurements of NOx from London suggest significantly higher emissions than predicted by inventories." Faraday Discussions 189 (2016): 455–72. http://dx.doi.org/10.1039/c5fd00170f.
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To date, direct validation of city-wide emissions inventories for air pollutants has been difficult or impossible. However, recent technological innovations now allow direct measurement of pollutant fluxes from cities, for comparison with emissions inventories, which are themselves commonly used for prediction of current and future air quality and to help guide abatement strategies. Fluxes of NOx were measured using the eddy-covariance technique from an aircraft flying at low altitude over London. The highest fluxes were observed over central London, with lower fluxes measured in suburban areas. A footprint model was used to estimate the spatial area from which the measured emissions occurred. This allowed comparison of the flux measurements to the UK's National Atmospheric Emissions Inventory (NAEI) for NOx, with scaling factors used to account for the actual time of day, day of week and month of year of the measurement. The comparison suggests significant underestimation of NOx emissions in London by the NAEI, mainly due to its under-representation of real world road traffic emissions. A comparison was also carried out with an enhanced version of the inventory using real world driving emission factors and road measurement data taken from the London Atmospheric Emissions Inventory (LAEI). The measurement to inventory agreement was substantially improved using the enhanced version, showing the importance of fully accounting for road traffic, which is the dominant NOx emission source in London. In central London there was still an underestimation by the inventory of 30–40% compared with flux measurements, suggesting significant improvements are still required in the NOx emissions inventory.
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Luhar, Ashok K., Ian E. Galbally, Matthew T. Woodhouse, and Nathan Luke Abraham. "Assessing and improving cloud-height-based parameterisations of global lightning flash rate, and their impact on lightning-produced NO<sub><i>x</i></sub> and tropospheric composition in a chemistry–climate model." Atmospheric Chemistry and Physics 21, no. 9 (May 10, 2021): 7053–82. http://dx.doi.org/10.5194/acp-21-7053-2021.
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Abstract. Although lightning-generated oxides of nitrogen (LNOx) account for only approximately 10 % of the global NOx source, they have a disproportionately large impact on tropospheric photochemistry due to the conducive conditions in the tropical upper troposphere where lightning is mostly discharged. In most global composition models, lightning flash rates used to calculate LNOx are expressed in terms of convective cloud-top height via the Price and Rind (1992) (PR92) parameterisations for land and ocean, where the oceanic parameterisation is known to greatly underestimate flash rates. We conduct a critical assessment of flash-rate parameterisations that are based on cloud-top height and validate them within the Australian Community Climate and Earth System Simulator – United Kingdom Chemistry and Aerosol (ACCESS-UKCA) global chemistry–climate model using the Lightning Imaging Sensor and Optical Transient Detector (LIS/OTD) satellite data. While the PR92 parameterisation for land yields satisfactory predictions, the oceanic parameterisation, as expected, underestimates the observed flash-rate density severely, yielding a global average over the ocean of 0.33 flashes s−1 compared to the observed 9.16 flashes s−1 and leading to LNOx being underestimated proportionally. We formulate new flash-rate parameterisations following Boccippio's (2002) scaling relationships between thunderstorm electrical generator power and storm geometry coupled with available data. The new parameterisation for land performs very similarly to the corresponding PR92 one, as would be expected, whereas the new oceanic parameterisation simulates the flash-rate observations much more accurately, giving a global average over the ocean of 8.84 flashes s−1. The use of the improved flash-rate parameterisations in ACCESS-UKCA changes the modelled tropospheric composition – global LNOx increases from 4.8 to 6.6 Tg N yr−1; the ozone (O3) burden increases by 8.5 %; there is an increase in the mid- to upper-tropospheric NOx by as much as 40 pptv, a 13 % increase in the global hydroxyl radical (OH), a decrease in the methane lifetime by 6.7 %, and a decrease in the lower-tropospheric carbon monoxide (CO) by 3 %–7 %. Compared to observations, the modelled tropospheric NOx and ozone in the Southern Hemisphere and over the ocean are improved by this new flash-rate parameterisation.
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Fatahi, Yalda, Rostislav Kouznetsov, and Mikhail Sofiev. "The effect of accounting for public holidays on the skills of the atmospheric composition model SILAM v.5.7." Geoscientific Model Development 14, no. 12 (December 7, 2021): 7459–75. http://dx.doi.org/10.5194/gmd-14-7459-2021.
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Abstract. This study quantifies the impact of emission changes during public holidays on air quality (AQ) and analyses the added value of accounting for the holidays in AQ modelling. Spatial and temporal distributions of atmospheric concentrations of the major air pollutants (the main focus was on NO2, but we also included O3, CO, PM2.5, and SO2) were considered at the European scale for all public holidays of 2018. Particular attention was paid to the events with the most pronounced continental- or regional-scale impact: Christmas and New Year, Easter, May Day vacations, and the last days of Ramadan. The simulations were performed with the chemistry transport model SILAM v.5.7 (System for Integrated modeLling of Atmospheric coMposition). Three model runs were made: the baseline with no treatment of holidays, the run considering holidays as Sundays, and the run forcing 80 % reduction in emissions during holidays for the weekday-sensitive sectors. The emission scaling was applied on a country basis. The model predictions were compared with in situ observations collected by the European Environment Agency. The experiment showed that even conservative treatment of official holidays has a large positive impact on NOx (up to 30 % of reduction in the bias inhomogeneity during the holiday days) and improves the CO, PM2.5, and O3 predictions. In many cases, the sensitivity simulations suggested a greater emission reduction than the level of Sundays. An individual consideration of the holiday events in different countries may further improve their representation in the models: specific diurnal pattern of emissions, additional emission due to fireworks, and different driving patterns.
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Kang, Daiwen, Christian Hogrefe, Golam Sarwar, James D. East, J. Mike Madden, Rohit Mathur, and Barron H. Henderson. "Assessing the Impact of Lightning NOx Emissions in CMAQ Using Lightning Flash Data from WWLLN over the Contiguous United States." Atmosphere 13, no. 8 (August 6, 2022): 1248. http://dx.doi.org/10.3390/atmos13081248.
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Comparison of lightning flash data from the National Lightning Detection Network (NLDN) and from the World Wide Lightning Location Network (WWLLN) over the contiguous United States (CONUS) for the 2016–2018 period reveals temporally and spatially varying flash rates that would influence lightning NOx (LNOx) production due to known detection efficiency differences especially during summer months over land (versus over ocean). However, the lightning flash density differences between the two networks show persistent seasonal patterns over geographical regions (e.g., land versus ocean). Since the NLDN data are considered to have higher accuracy (lightning detection with >95% efficiency), we developed scaling factors for the WWLLN flash data based on the ratios of WWLLN to NLDN flash data over time (months of year) and space. In this study, sensitivity simulations using the Community Multiscale Air Quality (CMAQ) model are performed utilizing the original data sets (both NLDN and WWLLN) and the scaled WWLLN flash data for LNOx production over the CONUS. The model performance of using the different lightning flash datasets for ambient O3 and NOx mixing ratios that are directly impacted by LNOx emissions and the wet and dry deposition of oxidized nitrogen species that are indirectly impacted by LNOx emissions is assessed based on comparisons with ground-based observations, vertical profile measurements, and satellite products. During summer months, the original WWLLN data produced less LNOx emissions (due to its lower lightning detection efficiency) compared to the NLDN data, which resulted in less improvement in model performance than the simulation using NLDN data as compared to the simulation without any LNOx emissions. However, the scaled WWLLN data produced LNOx estimates and model performance comparable with the NLDN data, suggesting that scaled WWLLN may be used as a substitute for the NLDN data to provide LNOx estimates in air quality models when the NLDN data are not available (e.g., due to prohibitive cost or lack of spatial coverage).
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Stufflebeam, J. H., D. W. Kendrick, W. A. Sowa, and T. S. Snyder. "Quantifying Fuel/Air Unmixedness in Premixing Nozzles Using an Acetone Fluorescence Technique." Journal of Engineering for Gas Turbines and Power 124, no. 1 (March 1, 1999): 39–45. http://dx.doi.org/10.1115/1.1396840.
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The ability of a lean-premixed combustion system to minimize emissions while maintaining combustion stability over the operating curve relies upon how well the fuel nozzle premixes the fuel and air. As the level of premixing increases, NOx emissions at a given flame temperature decrease until a perfectly premixed condition is achieved. The objective of this paper is to quantify the level of premixing achieved by a premixing nozzle using an acetone fluorescence technique and determine its relationship to NOx emissions and combustion stability. The technique of using acetone fluorescence has been used as a fast and quantitative diagnostic to map the fuel-air distribution. This technique has been applied to the development of a lean premixing nozzle to measure the fuel air distribution at the fuel nozzle exit plane. In this study, the fuel air distribution is presented as two-dimensional images. The average fuel/air ratio and the standard deviation are calculated at various annular regions to determine the distribution as a function of radius. A single unmixedness parameter (σ/μ) over the entire annulus is also calculated to allow relative ranking of the various fuel nozzle configurations. The fluorescence data is acquired for various nozzle hardware configurations in an atmospheric test facility. Fuel and air flow conditions are determined by scaling engine conditions to cold flow conditions and matching the fuel to air momentum ratio at the fuel injection site. Measured fuel/air distributions, six mm downstream of the nozzle exit plane, from the acetone fluorescence technique are correlated to emissions and acoustic measurements made at full pressure and temperature conditions in a single-nozzle test rig. The paper includes a description of the acetone fluorescence technique, the method for optimizing the fuel/air distribution through changes to the main gas fuel injection array, and correlations made between the fuel/air distribution, nozzle geometry, power setting, emissions, and combustor acoustics.
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McDuffie, Erin E., Steven J. Smith, Patrick O'Rourke, Kushal Tibrewal, Chandra Venkataraman, Eloise A. Marais, Bo Zheng, Monica Crippa, Michael Brauer, and Randall V. Martin. "A global anthropogenic emission inventory of atmospheric pollutants from sector- and fuel-specific sources (1970–2017): an application of the Community Emissions Data System (CEDS)." Earth System Science Data 12, no. 4 (December 15, 2020): 3413–42. http://dx.doi.org/10.5194/essd-12-3413-2020.
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Abstract. Global anthropogenic emission inventories remain vital for understanding the sources of atmospheric pollution and the associated impacts on the environment, human health, and society. Rapid changes in today's society require that these inventories provide contemporary estimates of multiple atmospheric pollutants with both source sector and fuel type information to understand and effectively mitigate future impacts. To fill this need, we have updated the open-source Community Emissions Data System (CEDS) (Hoesly et al., 2019) to develop a new global emission inventory, CEDSGBD-MAPS. This inventory includes emissions of seven key atmospheric pollutants (NOx; CO; SO2; NH3; non-methane volatile organic compounds, NMVOCs; black carbon, BC; organic carbon, OC) over the time period from 1970–2017 and reports annual country-total emissions as a function of 11 anthropogenic sectors (agriculture; energy generation; industrial processes; on-road and non-road transportation; separate residential, commercial, and other sectors (RCO); waste; solvent use; and international shipping) and four fuel categories (total coal, solid biofuel, the sum of liquid-fuel and natural-gas combustion, and remaining process-level emissions). The CEDSGBD-MAPS inventory additionally includes monthly global gridded (0.5∘ × 0.5∘) emission fluxes for each compound, sector, and fuel type to facilitate their use in earth system models. CEDSGBD-MAPS utilizes updated activity data, updates to the core CEDS default scaling procedure, and modifications to the final procedures for emissions gridding and aggregation. Relative to the previous CEDS inventory (Hoesly et al., 2018), these updates extend the emission estimates from 2014 to 2017 and improve the overall agreement between CEDS and two widely used global bottom-up emission inventories. The CEDSGBD-MAPS inventory provides the most contemporary global emission estimates to date for these key atmospheric pollutants and is the first to provide global estimates for these species as a function of multiple fuel types and source sectors. Dominant sources of global NOx and SO2 emissions in 2017 include the combustion of oil, gas, and coal in the energy and industry sectors as well as on-road transportation and international shipping for NOx. Dominant sources of global CO emissions in 2017 include on-road transportation and residential biofuel combustion. Dominant global sources of carbonaceous aerosol in 2017 include residential biofuel combustion, on-road transportation (BC only), and emissions from the waste sector. Global emissions of NOx, SO2, CO, BC, and OC all peak in 2012 or earlier, with more recent emission reductions driven by large changes in emissions from China, North America, and Europe. In contrast, global emissions of NH3 and NMVOCs continuously increase between 1970 and 2017, with agriculture as a major source of global NH3 emissions and solvent use, energy, residential, and the on-road transport sectors as major sources of global NMVOCs. Due to similar development methods and underlying datasets, the CEDSGBD-MAPS emissions are expected to have consistent sources of uncertainty as other bottom-up inventories. The CEDSGBD-MAPS source code is publicly available online through GitHub: https://github.com/emcduffie/CEDS/tree/CEDS_GBD-MAPS (last access: 1 December 2020). The CEDSGBD-MAPS emission inventory dataset (both annual country-total and monthly global gridded files) is publicly available under https://doi.org/10.5281/zenodo.3754964 (McDuffie et al., 2020c).
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De Nunzio, Giovanni, Mohamed Laraki, and Laurent Thibault. "Road Traffic Dynamic Pollutant Emissions Estimation: From Macroscopic Road Information to Microscopic Environmental Impact." Atmosphere 12, no. 1 (December 31, 2020): 53. http://dx.doi.org/10.3390/atmos12010053.
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Air pollution poses a major threat to health and climate, yet cities lack simple tools to quantify the costs and effects of their measures and assess those that are most effective in improving air quality. In this work, a complete modeling framework to estimate road traffic microscopic pollutant emissions from common macroscopic road and traffic information is proposed. A machine learning model to estimate driving behavior as a function of traffic conditions and road infrastructure is coupled with a physics-based microscopic emissions model. The up-scaling of the individual vehicle emissions to the traffic-level contribution is simply performed via a meta-model using both statistical vehicles fleet composition and traffic volume data. Validation results with real-world driving data show that: the driving behavior model is able to maintain an estimation error below 10% for relevant boundary parameter of the speed profiles (i.e., mean, initial, and final speed) on any road segment; the traffic microscopic emissions model is able to reduce the estimation error by more than 50% with respect to reference macroscopic models for major pollutants such as NOx and CO2. Such a high-resolution road traffic emissions model at the scale of every road segment in the network proves to be highly beneficial as a source for air quality models and as a monitoring tool for cities.
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Gopalan, Anantha-Iyengar, Jun-Cheol Lee, Gopalan Saianand, Kwang-Pill Lee, Prashant Sonar, Rajarathnam Dharmarajan, Yao-long Hou, Ki-Yong Ann, Venkatramanan Kannan, and Wha-Jung Kim. "Recent Progress in the Abatement of Hazardous Pollutants Using Photocatalytic TiO2-Based Building Materials." Nanomaterials 10, no. 9 (September 16, 2020): 1854. http://dx.doi.org/10.3390/nano10091854.
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Titanium dioxide (TiO2) has been extensively investigated in interdisciplinary research (such as catalysis, energy, environment, health, etc.) owing to its attractive physico-chemical properties, abundant nature, chemical/environmental stability, low-cost manufacturing, low toxicity, etc. Over time, TiO2-incorporated building/construction materials have been utilized for mitigating potential problems related to the environment and human health issues. However, there are challenges with regards to photocatalytic efficiency improvements, lab to industrial scaling up, and commercial product production. Several innovative approaches/strategies have been evolved towards TiO2 modification with the focus of improving its photocatalytic efficiency. Taking these aspects into consideration, research has focused on the utilization of many of these advanced TiO2 materials towards the development of construction materials such as concrete, mortar, pavements, paints, etc. This topical review focuses explicitly on capturing and highlighting research advancements in the last five years (mainly) (2014–2019) on the utilization of various modified TiO2 materials for the development of practical photocatalytic building materials (PBM). We briefly summarize the prospective applications of TiO2-based building materials (cement, mortar, concretes, paints, coating, etc.) with relevance to the removal of outdoor/indoor NOx and volatile organic compounds, self-cleaning of the surfaces, etc. As a concluding remark, we outline the challenges and make recommendations for the future outlook of further investigations and developments in this prosperous area.
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Behrendt, T., P. R. Veres, F. Ashuri, G. Song, M. Flanz, B. Mamtimin, M. Bruse, J. Williams, and F. X. Meixner. "Characterisation of NO production and consumption: new insights by an improved laboratory dynamic chamber technique." Biogeosciences Discussions 11, no. 1 (January 17, 2014): 1187–275. http://dx.doi.org/10.5194/bgd-11-1187-2014.
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Abstract. Biogenic NOx emissions from natural and anthropogenically influenced soils are currently estimated to amount to 9 Tg a−1, hence a significant fraction of global NOx emissions (45 Tg a−1). During the last three decades, a large number of field measurements have been performed to quantify biogenic NO emissions. To study biogenic NO emissions as a function of soil moisture, soil temperature, and soil nutrients, several laboratory approaches have been developed to estimate local/regional NO emissions by suitable up-scaling. This study presents an improved and automated laboratory dynamic chamber system (consisting of six individual soil chambers) for investigation and quantification of all quantities necessary to characterize biogenic NO release from soil (i.e., net NO release rate, NO production and consumption rate, and respective Q10 values). In contrast to former versions of the laboratory dynamic chamber system, the four experiments for complete characterization can now be performed on a single soil sample, whereas former studies had to be performed on four sub-samples. This study discovered that the sub-sample variability biased former measurements of net NO release rates tremendously. Furthermore, it was also shown that the previously reported variation of optimum soil moisture (i.e., where a maximum net NO release rate occurs) between individual sub-samples is most likely a methodical artefact of former versions of the laboratory dynamic chamber system. A comprehensive and detailed methodical concept description of the improved laboratory dynamic chamber system is provided. Response of all quantities (necessary to characterize net NO release) to soil temperature and NO mixing ratio of the flushing air-stream are determined by automatic monitoring of these variables during one single drying-out experiment with one single soil sample only. The method requires precise measurements of NO mixing ratio at the inlet and outlet of each soil chamber; finally, four pairs of inlet/outlet NO mixing ratios are sufficient to derive all necessary quantities. Soil samples from drylands exhibit particularly low NO production, but even lower NO consumption rates. However, with the improved laboratory dynamic chamber system those low levels can be quantified, as well as corresponding NO compensation point mixing ratios and respective Q10 values. It could be shown, that the NO compensation point mixing ratio seems to be generally independent of gravimetric soil moisture content, but, particularly for dryland soils, strongly dependent on soil temperature. New facilities have been included into the improved system (e.g. for investigation of net release rates of other trace gases, namely CO2 and VOCs). First results are shown for net release rates of acetone (C3H6O), acetaldehyde (C2H4O) and CO2. This new system is thus able to simultaneously investigate potential mechanistic links between NO, multitudinous VOC and CO2.
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Lee-Taylor, J., S. Madronich, B. Aumont, M. Camredon, A. Hodzic, G. S. Tyndall, E. Apel, and R. A. Zaveri. "Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume." Atmospheric Chemistry and Physics Discussions 11, no. 6 (June 20, 2011): 17013–70. http://dx.doi.org/10.5194/acpd-11-17013-2011.
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Abstract. The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3–10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15–20 μg m−3, and SOA peaking at 10–15 μg m−3 during mid-day. The majority (≥75 %) of the model SOA stems from the large n-alkanes, with the remainder mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by δ-hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.
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Lee-Taylor, J., S. Madronich, B. Aumont, A. Baker, M. Camredon, A. Hodzic, G. S. Tyndall, E. Apel, and R. A. Zaveri. "Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume." Atmospheric Chemistry and Physics 11, no. 24 (December 21, 2011): 13219–41. http://dx.doi.org/10.5194/acp-11-13219-2011.
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Abstract. The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3-10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15–20 μg m−3, and SOA peaking at 10–15 μg m−3 during mid-day. The majority (≥75%) of the model SOA stems from reaction products of the large n-alkanes, used here as surrogates for all emitted hydrocarbons of similar volatility, with the remaining SOA originating mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by δ-hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.
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Hoor, P., J. Borken-Kleefeld, D. Caro, O. Dessens, O. Endresen, M. Gauss, V. Grewe, et al. "The impact of traffic emissions on atmospheric ozone and OH: results from QUANTIFY." Atmospheric Chemistry and Physics 9, no. 9 (May 14, 2009): 3113–36. http://dx.doi.org/10.5194/acp-9-3113-2009.
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Abstract. To estimate the impact of emissions by road, aircraft and ship traffic on ozone and OH in the present-day atmosphere six different atmospheric chemistry models have been used. Based on newly developed global emission inventories for road, ship and aircraft emission data sets each model performed sensitivity simulations reducing the emissions of each transport sector by 5%. The model results indicate that on global annual average lower tropospheric ozone responds most sensitive to ship emissions (50.6%±10.9% of the total traffic induced perturbation), followed by road (36.7%±9.3%) and aircraft exhausts (12.7%±2.9%), respectively. In the northern upper troposphere between 200–300 hPa at 30–60° N the maximum impact from road and ship are 93% and 73% of the maximum effect of aircraft, respectively. The latter is 0.185 ppbv for ozone (for the 5% case) or 3.69 ppbv when scaling to 100%. On the global average the impact of road even dominates in the UTLS-region. The sensitivity of ozone formation per NOx molecule emitted is highest for aircraft exhausts. The local maximum effect of the summed traffic emissions on the ozone column predicted by the models is 0.2 DU and occurs over the northern subtropical Atlantic extending to central Europe. Below 800 hPa both ozone and OH respond most sensitively to ship emissions in the marine lower troposphere over the Atlantic. Based on the 5% perturbation the effect on ozone can exceed 0.6% close to the marine surface (global zonal mean) which is 80% of the total traffic induced ozone perturbation. In the southern hemisphere ship emissions contribute relatively strongly to the total ozone perturbation by 60%–80% throughout the year. Methane lifetime changes against OH are affected strongest by ship emissions up to 0.21 (± 0.05)%, followed by road (0.08 (±0.01)%) and air traffic (0.05 (± 0.02)%). Based on the full scale ozone and methane perturbations positive radiative forcings were calculated for road emissions (7.3±6.2 mWm−2) and for aviation (2.9±2.3 mWm−2). Ship induced methane lifetime changes dominate over the ozone forcing and therefore lead to a net negative forcing (−25.5±13.2 mWm−2).
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Johnson, David, Michael E. Jenkin, Klaus Wirtz, and Montserrat Martin-Reviejo. "Simulating the Formation of Secondary Organic Aerosol from the Photooxidation of Aromatic Hydrocarbons." Environmental Chemistry 2, no. 1 (2005): 35. http://dx.doi.org/10.1071/en04079.
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Environmental Context. Atmospheric particulate material can affect the radiative balance of the atmosphere and is believed to be detrimental to human health. Secondary organic aerosols (SOA), which make a significant contribution to the total atmospheric burden of fine particulate material, are formed in situ following the photochemical transformation of organic pollutants into relatively less-volatile, oxygenated compounds which can subsequently transfer from the gas phase to a particle phase. SOA formation from the atmospheric photooxidation of aromatic hydrocarbons—present, for example, as a result of automobile use—is believed to be important in the urban environment and yet the mechanisms are not well understood. For example, even the reasons for observed variations in the relative propensity for SOA formation, from the photooxidation of various simple aromatic hydrocarbons, are not clear. Abstract. The formation and composition of secondary organic aerosol (SOA) from the photooxidation of benzene, p-xylene, and 1,3,5-trimethylbenzene has been simulated using the Master Chemical Mechanism version 3.1 (MCM v3.1) coupled to a representation of the transfer of organic material from the gas to particle phase. The combined mechanism was tested against data obtained from a series of experiments conducted at the European Photoreactor (EUPHORE) outdoor smog chamber in Valencia, Spain. Simulated aerosol mass concentrations compared reasonably well with the measured SOA data only after absorptive partitioning coefficients were increased by a factor of between 5 and 30. The requirement of such scaling was interpreted in terms of the occurrence of unaccounted-for association reactions in the condensed organic phase leading to the production of relatively more nonvolatile species. Comparisons were made between the relative aerosol forming efficiencies of benzene, toluene, p-xylene, and 1,3,5-trimethylbenzene, and differences in the OH-initiated degradation mechanisms of these aromatic hydrocarbons. A strong, nonlinear relationship was observed between measured (reference) yields of SOA and (proportional) yields of unsaturated dicarbonyl aldehyde species resulting from ring-fragmenting pathways. This observation, and the results of the simulations, is strongly suggestive of the involvement of reactive aldehyde species in association reactions occurring in the aerosol phase, thus promoting SOA formation and growth. The effect of NOx concentrations on SOA formation efficiencies (and formation mechanisms) is discussed.
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Dopson, Laurence. "Scaling the heights." Nursing Older People 16, no. 7 (October 2004): 47. http://dx.doi.org/10.7748/nop.16.7.47.s24.
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Marrapu, P., Y. Cheng, G. Beig, S. Sahu, R. Srinivas, and G. R. Carmichael. "Air quality in Delhi during the CommonWealth Games." Atmospheric Chemistry and Physics Discussions 14, no. 7 (April 17, 2014): 10025–59. http://dx.doi.org/10.5194/acpd-14-10025-2014.
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Abstract. Air quality during The CommonWealth Games (CWG, held in Delhi in October 2010) is analyzed using a new air quality forecasting system established for the Games. The CWG stimulated enhanced efforts to monitor and model air quality in the region. The air quality of Delhi during the CWG had high levels of particles with mean values of PM2.5 and PM10 at the venues of 111 and 238 μg m−3, respectively. Black carbon (BC) accounted for ∼10% of the PM2.5 mass. It is shown that BC, PM2.5 and PM10 concentrations are well predicted, but with positive biases of ∼25%. The diurnal variations are also well captured, with both the observations and the modeled values showing nighttime maxima and daytime minima. A new emissions inventory, developed as part of this air quality forecasting initiative, is evaluated by comparing the observed and predicted species-species correlations (i.e., BC : CO; BC : PM2.5; PM2.5 : PM10). Assuming that the observations at these sites are representative and that all the model errors are associated with the emissions, then the modeled concentrations and slopes can be made consistent by scaling the emissions by: 0.6 for NOx, 2 for CO, and 0.7 for BC, PM2.5 and PM10. The emission estimates for particles are remarkably good considering the uncertainty in the estimates due to the diverse spread of activities and technologies that take place in Delhi and the rapid rates of change. The contribution of various emission sectors including transportation, power, domestic and industry to surface concentrations are also estimated. Transport, domestic and industrial sectors all make significant contributions to PM levels in Delhi, and the sectoral contributions vary spatially within the city. Ozone levels in Delhi are elevated, with hourly values sometimes exceeding 100 ppb. The continued growth of the transport sector is expected to make ozone pollution a more pressing air pollution problem in Delhi. The sector analysis provides useful inputs into the design of strategies to reduce air pollution levels in Delhi. The contribution for sources outside of Delhi on Delhi air quality range from ∼25% for BC and PM to ∼60% for day time ozone. The significant contributions from non-Delhi sources indicates that in Delhi (as has been show elsewhere) these strategies will also need a more regional perspective.
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Marrapu, P., Y. Cheng, G. Beig, S. Sahu, R. Srinivas, and G. R. Carmichael. "Air quality in Delhi during the Commonwealth Games." Atmospheric Chemistry and Physics 14, no. 19 (October 9, 2014): 10619–30. http://dx.doi.org/10.5194/acp-14-10619-2014.
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Abstract. Air quality during the Commonwealth Games (CWG, held in Delhi in October 2010) is analyzed using a new air quality forecasting system established for the games. The CWG stimulated enhanced efforts to monitor and model air quality in the region. The air quality of Delhi during the CWG had high levels of particles with mean values of PM2.5 and PM10 at the venues of 111 and 238 μg m−3, respectively. Black carbon (BC) accounted for ~ 10% of the PM2.5 mass. It is shown that BC, PM2.5 and PM10 concentrations are well predicted, but with positive biases of ~ 25%. The diurnal variations are also well captured, with both the observations and the modeled values showing nighttime maxima and daytime minima. A new emissions inventory, developed as part of this air quality forecasting initiative, is evaluated by comparing the observed and predicted species-species correlations (i.e., BC : CO; BC : PM2.5; PM2.5 : PM10). Assuming that the observations at these sites are representative and that all the model errors are associated with the emissions, then the modeled concentrations and slopes can be made consistent by scaling the emissions by 0.6 for NOx, 2 for CO, and 0.7 for BC, PM2.5, and PM10. The emission estimates for particles are remarkably good considering the uncertainty in the estimates due to the diverse spread of activities and technologies that take place in Delhi and the rapid rates of change. The contribution of various emission sectors including transportation, power, domestic and industry to surface concentrations are also estimated. Transport, domestic and industrial sectors all make significant contributions to PM levels in Delhi, and the sectoral contributions vary spatially within the city. Ozone levels in Delhi are elevated, with hourly values sometimes exceeding 100 ppb. The continued growth of the transport sector is expected to make ozone pollution a more pressing air pollution problem in Delhi. The sector analysis provides useful inputs into the design of strategies to reduce air pollution levels in Delhi. The contribution for sources outside of Delhi on Delhi air quality range from ~ 25% for BC and PM to ~ 60% for day time ozone. The significant contributions from non-Delhi sources indicates that in Delhi (as has been show elsewhere) these strategies will also need a more regional perspective.
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Blechschmidt, Anne-Marlene, Joaquim Arteta, Adriana Coman, Lyana Curier, Henk Eskes, Gilles Foret, Clio Gielen, et al. "Comparison of tropospheric NO<sub>2</sub> columns from MAX-DOAS retrievals and regional air quality model simulations." Atmospheric Chemistry and Physics 20, no. 5 (March 6, 2020): 2795–823. http://dx.doi.org/10.5194/acp-20-2795-2020.
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Abstract. Multi-axis differential optical absorption spectroscopy (MAX-DOAS) tropospheric NO2 column retrievals from four European measurement stations are compared to simulations from five regional air quality models which contribute to the European regional ensemble forecasts and reanalyses of the operational Copernicus Atmosphere Monitoring Service (CAMS). Compared to other observational data usually applied for regional model evaluation, MAX-DOAS data are closer to the regional model data in terms of horizontal and vertical resolution, and multiple measurements are available during daylight, so that, for example, diurnal cycles of trace gases can be investigated. In general, there is good agreement between simulated and retrieved NO2 column values for individual MAX-DOAS measurements with correlations between 35 % and 70 % for individual models and 45 % to 75 % for the ensemble median for tropospheric NO2 vertical column densities (VCDs), indicating that emissions, transport and tropospheric chemistry of NOx are on average well simulated. However, large differences are found for individual pollution plumes observed by MAX-DOAS. Most of the models overestimate seasonal cycles for the majority of MAX-DOAS sites investigated. At the urban stations, weekly cycles are reproduced well, but the decrease towards the weekend is underestimated and diurnal cycles are overall not well represented. In particular, simulated morning rush hour peaks are not confirmed by MAX-DOAS retrievals, and models fail to reproduce observed changes in diurnal cycles for weekdays versus weekends. The results of this study show that future model development needs to concentrate on improving representation of diurnal cycles and associated temporal scalings.