Simulated Ozone Concentrations Research Articles

REGIONAL-SCALE MODELING OZONE AIR QUALITY OVER THE CONTINENTAL SOUTH EAST ASIA

Long range transport of ozone and its precursors can significantly impact the air quality in downwind regions. The problem of regional transport of ozone has been studied for more than three decades in Europe and U.S but not yet in Southeast Asia. This study investigated the regional scale distribution of tropospheric ozone over the Continental South East Asia Region (CSEA) of Thailand, Burma, Cambodia, Lao and Vietnam. The Models-3 Community Multi-scale Air Quality (CMAQ modeling system, driven by the NCAR/Penn State Fifth-Generation Mesoscale Model (MM5), is used for the purpose. The model domain covers the longitude range from 91'E to 111°E and the latitude range from 5°N to 25°N. Two most recent ozone episodes of March 24-26, 2004 and January 2-4, 2005 were selected which represent the typical meteorological conditions for high ozone concentrations periods of a year. The episode analysis was made based on available data from 10 and 4 monitoring stations located in Bangkok of Thailand and Ho Chi Minh City (HCMC) of Vietnam, respectively. The episodes were characterized with hourly ozone levels above the National Ambient Air Quality Standards of Thailand and Vietnam of 100 ppb at a number of the monitoring stations. The maximum ground level concentrations of ozone for March 2004 and January 2005 episodes reached 173 ppb and 157 ppb, respectively, in the urban plume of the Bangkok Metropolitan Region (BMR). The simulations were performed with 0.5o 0.5° emission input data which was prepared from the regional anthropogenic emission inventory used in the Transport and Chemical Evolution over the Pacific (TRACE-P), and the biogenic emissions obtained from the Global Emissions Inventory Activity (GEIA). The simulated overall picture of ground level ozone concentrations over CSEA domain shows that the concentrations were high at the downwind areas at a considerable distance from large urban areas such as BMR and HCMC. During March 2004 episode the ozone plume moved northeastward following the Southwesterly monsoon and the maximum width of the modeled plume with the ozone above 100 ppb was about 70 km from BMR. For HCMC the ozone plume moved northward and the concentration in the city plume was lower with the width of isopleth of 50ppb of around 40 km. During the Jan 2005 episode the ozone plume moved southwestward following the Northeasterly monsoon and the width of the modeled plume with the ozone concentration above 100 ppb in BMR was 50 km while for HCMC the width of the 40ppb isopleth was about 30 km. The model performance was evaluated on the available observed hourly ozone concentrations. The model system was shown to be able to reproduce the peak ozone levels that occurred during the episodes at these two large urban areas, and capture the day by day variations during the selected episodes. The performance statistics MNBE, NGE, and UPA for the simulated ozone concentrations are within U.S. EPA guidance criteria and are comparable to those reported previous for other regional ozone simulations. It is shown that the MM5/CMAQ system is the suitable modeling tools for ozone prediction over the CSEA.

High-resolution modeling and evaluation of ozone air quality of Osaka using MM5-CMAQ system

High-resolution modeling approach is increasingly being considered as a necessary step for improving the monitoring and predictions of regional air quality. This is especially true for highly urbanized region with complex terrain and land-use. This study uses Community Multiscale Air Quality (CMAQ) model coupled with MM5 mesoscale model for a comprehensive analysis to assess the suitability of such high-resolution modeling system in predicting ozone air quality in the complex terrains of Osaka, Japan. The 1-km and 3-km grid domains were nested inside a 9-km domain and the domain with 1-km grid covered the Osaka region. High-resolution Grid Point Value-Mesoscale Model (GPV-MSM) data were used after suitable validation. The simulated ozone concentrations were validated and evaluated using statistical metrics using performance criteria set for ozone. Daily maxima of ozone were found better simulated by the 1-km grid domain than the coarser 9-km and 3-km domains, with the maximum improvement in the mean absolute gross error about 3 ppbv. In addition, 1-km grid results fared better than other grids at most of the observation stations that showed noticeable differences in gross error as well as correlation. These results amply justify the use of the integrated high-resolution MM5-CMAQ modeling system in the highly urbanized region, such as the Osaka region, which has complex terrain and land-use.

Meso-urban meteorological and photochemical modeling of heat island mitigation

A fine-resolution, meso-urban meteorological model was updated and applied, using new data and techniques in this study, in driving fine-resolution photochemical simulations to evaluate the air-quality impacts of urban heat island mitigation. The drag-force-based formulation of the model improves the simulation of fine-resolution meteorological and air-pollutant concentration fields in the urban canopy layer. Compared to the meso scale, the meso-urban modeling of heat island mitigation produces larger localized impacts on meteorology and ozone air quality and captures phenomena of interest that are typically not detectable at the coarser scale. These include, for example, cool islands, heat islands, flow convergence associated with heat island circulation, flow divergence at the leading edge of urban areas, and vertical variation in turbulent kinetic energy budget components within the canopy layer in response to vertical changes in densities of buildings and vegetation. They also include fine-resolution features in the simulated ozone concentration field and its response to surface modifications. Model results show that heat island mitigation is effective in reducing local ozone concentrations. This paper presents results from Sacramento, California, as an example using increased urban albedo as the control mechanism. For the region, episodic conditions, and surface modification scenarios examined in this paper, air temperature is decreased by up to 3 °C. Changes in ozone consist overwhelmingly of decreases but can also involve increases with the latter being confined to small areas and short time intervals. While larger reductions in ozone are detected, decreases of up to 5–10 ppb are more representative and the daily maximum 8-h average can be decreased by up to 13%.

Sensitivity of Surface Ozone Simulation to Cumulus Parameterization

Abstract Different cumulus schemes cause significant discrepancies in simulated precipitation, cloud cover, and temperature, which in turn lead to remarkable differences in simulated biogenic volatile organic compound (BVOC) emissions and surface ozone concentrations. As part of an effort to investigate the impact (and its uncertainty) of climate changes on U.S. air quality, this study evaluates the sensitivity of BVOC emissions and surface ozone concentrations to the Grell (GR) and Kain–Fritsch (KF) cumulus parameterizations. Overall, using the KF scheme yields less cloud cover, larger incident solar radiation, warmer surface temperature, and higher boundary layer height and hence generates more BVOC emissions than those using the GR scheme. As a result, the KF (versus GR) scheme produces more than 10 ppb of summer mean daily maximum 8-h ozone concentration over broad regions, resulting in a doubling of the number of high-ozone occurrences. The contributions of meteorological conditions versus BVOC emissions on regional ozone sensitivities to the choice of the cumulus scheme largely offset each other in the California and Texas regions, but the contrast in BVOC emissions dominates over that in the meteorological conditions for ozone differences in the Midwest and Northeast regions. The result demonstrates the necessity of considering the uncertainty of future ozone projections that are identified with alternative model physics configurations.

Uncertainty evaluation of ozone production and its sensitivity to emission changes over the Ile‐de‐France region during summer periods

The approach of Bayesian Monte Carlo analysis has been used for evaluating model uncertainty in ozone production and its sensitivity to emission changes. This approach has been applied to the ozone fields calculated by the CHIMERE regional model in the Ile‐de‐France area during the 1998 and 1999 summer seasons. The AIRPARIF network measurements of urban NO and O3 concentrations and rural O3 over the Ile‐de‐France region have been used for constraining the Monte Carlo simulations. Our results yield the following major conclusions: (1) The simulated formation of O3 plumes are mainly located in southwestern to southeastern directions downwind the Paris area. (2) Uncertainties on simulated ozone concentrations and several derived quantities are evaluated and reduced using the BMC approach; simulated urban and plume ozone concentrations are enhanced through the observational constraint as compared to those obtained from the unconstrained model. (3) The chemical regime over the urban area of Paris and within plumes is clearly VOC sensitive on the average over two summers. This statement is robust with respect to the BMC uncertainty analysis.

The role of ozone atmosphere-snow gas exchange on polar, boundary-layer tropospheric ozone – a review and sensitivity analysis

Abstract. Recent research on snowpack processes and atmosphere-snow gas exchange has demonstrated that chemical and physical interactions between the snowpack and the overlaying atmosphere have a substantial impact on the composition of the lower troposphere. These observations also imply that ozone deposition to the snowpack possibly depends on parameters including the quantity and composition of deposited trace gases, solar irradiance, snow temperature and the substrate below the snowpack. Current literature spans a remarkably wide range of ozone deposition velocities (vdO3); several studies even reported positive ozone fluxes out of the snow. Overall, published values range from ~–3<vdO3<2 cm s−1, although most data are within 0<vdO3<0.2 cm s−1. This literature reveals a high uncertainty in the parameterization and the magnitude of ozone fluxes into (and possibly out of) snow-covered landscapes. In this study a chemistry and tracer transport model was applied to evaluate the applicability of the published vdO3 and to investigate the sensitivity of tropospheric ozone towards ozone deposition over Northern Hemisphere snow-covered land and sea-ice. Model calculations using increasing vdO3 of 0.0, 0.01, 0.05 and 0.10 cm s−1 resulted in general ozone sensitivities up to 20–30% in the Arctic surface layer, and of up to 130% local increases in selected Northern Latitude regions. The simulated ozone concentrations were compared with mean January ozone observations from 18 Arctic stations. Best agreement between the model and observations, not only in terms of absolute concentrations but also in the hourly ozone variability, was found by applying an ozone deposition velocity in the range of 0.00–0.01 cm s−1, which is smaller than most literature data and also significantly lower compared to the value of 0.05 cm s−1 that is commonly applied in large-scale atmospheric chemistry models. This sensitivity analysis demonstrates that large errors in the description of the wintertime tropospheric ozone budget stem from the uncertain magnitude of ozone deposition rates and the inability to properly parameterize ozone fluxes to snow-covered landscapes.

Past, present, and future concentrations of tropospheric ozone and aerosols: Methodology, ozone evaluation, and sensitivity to aerosol wet removal

Tropospheric ozone and aerosols are radiatively important trace species, whose concentrations have increased dramatically since preindustrial times and are projected to continue to change in the future. The evolution of ozone and aerosol concentrations from 1860 to 2100 is simulated on the basis of estimated historical emissions and four different future emission scenarios (Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios A2, A1B, B1, and A1FI). The simulations suggest that the tropospheric burden of ozone has increased by 50% and sulfate and carbonaceous aerosol burdens have increased by factors of 3 and 6, respectively, since preindustrial times. Projected ozone changes over the next century range from −6% to +43%, depending on the emissions scenario. Sulfate concentrations are projected to increase for the next several decades but then to decrease by 2100 to 4–45% below their 2000 values. Simulated ozone concentrations agree well with present‐day observations and recent trends. Preindustrial surface concentrations of ozone are shown to be sensitive to the assumed anthropogenic and biomass burning emissions, but in all cases they overestimate the few available measurements from that era. Simulated tropospheric burdens of aerosols are sensitive by up to a factor of 2 to assumptions about the rate of aerosol wet deposition in the model. The concentrations of ozone and aerosols produced by this study are provided as climate‐forcing agents in the Geophysical Fluid Dynamics Laboratory coupled climate model to estimate their effects on climate. The aerosol distributions from this study and the resulting optical depths are evaluated in a companion paper by P. Ginoux et al. (2006).

Influence of future climate and emissions on regional air quality in California

Using a chemical transport model simulating ozone concentrations in central California, we evaluate the effects of variables associated with future changes in climate and ozone precursor emissions, including (1) increasing temperature; (2) increasing atmospheric water vapor; (3) increasing biogenic VOC emissions due to temperature; (4) projected decreases in anthropogenic NOx, VOC, and CO emissions in California for 2050; and (5) the influence of changing ozone, CO, and methane at the western boundary. Climatic changes expected for temperature, atmospheric water vapor, and biogenic VOC emissions each individually cause a 1–5% increase in the daily peak ozone. Projected reductions in anthropogenic emissions of 10–50% in NOx and 50–70% in VOCs and CO have the greatest single effect, reducing ozone by 8–15% in urban areas. Changes to the chemical boundary conditions lead to ozone increases of 6% in the San Francisco Bay area and along the west coast but only 1–2% inland. Simulations combining climate effects predict that ozone will increase 3–10% in various regions of California. This increase is partly offset by projected future emissions reductions, and a combined climate and emissions simulation yields ozone reductions of 3–9% in the Central Valley and almost no net change in the San Francisco Bay area. We find that different portions of the model domain have widely varying sensitivity to climate parameters. In particular, the San Francisco Bay region is more strongly influenced by temperature changes than inland regions, indicating that air quality in this region may worsen under future climate regimes.

Sensitivity analysis by the adjoint chemistry transport model DRAISfor an episode in the Berlin Ozone (BERLIOZ) experiment

Abstract. The Berlin Ozone Experiment (BERLIOZ) was carried out in summer 1998. One of its purposes was the evaluation of Chemistry Transport Models (CTM). CTM KAMM/DRAIS was one of the models considered. The data of 20 July were selected for evaluation. On that day, a pronounced ozone plume developed downwind of the city. Evaluation showed that the KAMM/DRAIS model is able to reproduce the meteorological and ozone data observed, except at farther distances (60–80 km) downwind of the city. In that region, the DRAIS model underestimates the measured ozone concentrations by 10–15 ppb, approximately. Therefore, this study was conducted to detect possible reasons for this deviation. A comprehensive sensitivity analysis was carried out to determine the most relevant model parameters. The adjoint DRAIS model was developed for this purpose, because for this study the application of this model is the most effective method of calculating the sensitivities. The least squares of the measured and simulated ozone concentrations between 08:00 UTC and 16:00 UTC at two stations 30 km and 70 km downwind of the city centre were chosen as distance function. The model parameters considered in this study are the complete set of initial and boundary species concentrations, emissions, and reaction rates, respectively. A sensitivity ranking showing the relevance of the individual parameters in the set is determined for each parameter set. In order to find out which modification in the parameter sets most reduces the cost function, simplified 4-D data assimilation was carried out. The result of this data assimilation shows that modifications of the reaction rates provide the best agreement between the measured and the simulated ozone concentrations at both stations. However, the modified reaction rates seem to be unrealistic for the whole simulation period. Therefore, the good agreement should not be overestimated. The agreement is still acceptable when the parameters in the other sets are modified together. The investigation demonstrates that an analysis of this type can help to explain inconsistencies between observations and simulations. But in the case considered here the inconsistencies cannot be explained by an error in only one parameter set.

Simulation of ozone during the August 2003 heat wave and emission control scenarios

During August 2003, western European countries witnessed an unpreceeded 15-day long heat wave with record temperatures and unusually persistent high-ozone concentrations. In France, about 15 000 extra deaths occurred during this period. The study of photochemical smog during this episode is of primary interest since weather conditions were so extreme for western Europe that they provide a worst case scenario for air quality. This episode also provides an interesting benchmark for the evaluation air quality models. We present and evaluate the results of a regional simulation of the episode with the CHIMERE chemistry-transport model. In a reference run, the simulated ozone concentrations are compared to surface observations obtained from 237 monitoring stations in Europe. Statistical scores on diurnal cycle, daily maxima, spatial structure of ozone concentrations, and AOT60 show that the simulated values compare very well with the observed ones, although extreme ozone peaks are underestimated probably due to a lack of model resolution. We describe the simulated impacts on ozone of theoretical emission reduction scenarios. The current European legislation should lead in 2010 to a drastic reduction of health exposure (about half), as measured by the AOT60 indicator, and of the number of 180 mu g m(-3) exceedance hours (74 % reduction). Emergency scenarios, with an assumed 20% emission reduction throughout Europe, would also be efficient (AOT60 indicator reduced by 28 %). Over France, the efficiency of a national emergency scenario would be only about 2/3rd of that of a Europewide scenario. When the reduction starts after a few episode days, the time taken for the reduction to reach its full impact is about 3 days. Finally, it is shown that reduction of NO, emissions is twice as efficient as reduction in volatile organic compounds emissions.

Boundary-layer evolution over Phoenix, Arizona and the premature mixing of pollutants in the early morning

The 2001 Phoenix Sunrise campaign was a field measurement program to investigate the early morning chemical and meteorological processes associated with the development of ozone pollution in Phoenix, Arizona. As part of that study, atmospheric structure was measured using wind profiling radars, sodars, and radiosondes at several locations in the Phoenix metropolitan area. Chemical measurements made by other investigators showed that vertical mixing of pollutants began prior to sunrise on a number of occasions. This was surprising, since we expected sustained mixing to occur only after sunrise and the onset of solar heating. We have used the meteorological measurements to identify a density current that commonly arrives in downtown Phoenix in the hour or two before sunrise when conditions are undisturbed. Both winds and cold advection associated with this feature act to destabilize the lower atmosphere, and the resulting mixing continues through the morning transition to convective conditions. Because photochemical production of ozone is non-linearly dependent on the concentrations of precursor species, this early mixing will need to be properly represented in combined meteorological and chemical models if they are to be fully successful in simulating ozone concentrations.

Isoprene and monoterpenes biogenic emissions in France: modeling and impact during a regional pollution episode

Biogenic emission of isoprene and monoterpenes are modeled in order to study their impact on regional atmospheric chemistry and pollution in France. First, an emission potential inventory is developed using a fine scale landuse database, forest composition statistics, biometric data and species emission factors. Considering the main emission patterns, the results show consistency with previously published European and global inventories. When downscaling to sub-region of France, this database is likely to provide refined sources distribution, an important issue for regional atmospheric chemistry studies. The temporal evolution of biogenic fluxes with meteorological conditions is calculated on line in the MesoNH–C meso-scale atmospheric chemistry model. Leaf-level algorithms are integrated at the ecosystem scale using sub-grid prognostic surface temperature and canopy shading effects. Finally, ecosystem to landscape integration is performed by aggregating biogenic fluxes at the model grid cell scale. Uncertainties associated with these estimations are discussed with respect to different spatial scales. In the second part of the paper, these developments are used to study biogenic emission impacts on regional ozone formation. We focus on a summer pollution event over Paris and northern France, documented during the ESQUIF experiment. The introduction of biogenic fluxes led to an increase in simulated surface ozone concentrations, reaching 18–30% in the Paris plume and about 20–30% in some rural areas. This impact was mainly due to large biogenic fluxes as well as to the chemical conditions prevailing in the anthropogenic plumes reaching biogenic sources. In this situation, some comparisons with air quality measurements pointed out an improvement of simulated ozone concentrations when accounting for biogenic fluxes, both in urban plumes and over rural areas.

A development of ozone abatement strategies for the Grenoble area using modeling and indicators

Abstract The Grenoble metropolitan area, located in the French Alps, regularly has periods of high ozone concentrations during the summertime. Grenoble is located in a Y shaped convergence of three deep valleys, some 3000 m above sea level, with typical wind pattern. During the summer of 1999, a major field campaign GRENOble PHOTochemistry (GRENOPHOT) was held in order to obtain measurements necessary for air quality model validation. The air quality model METeorological PHOtochemistry MODel (METPHOMOD) is used to investigate the dynamic characteristics of air pollution in the Grenoble area during the GRENOPHOT field campaign. The meteorological and atmospheric chemistry simulations were validated using both ground and vertical profile measurements (e.g. lidar) performed during the observation period (25–27 July) when the measured ozone concentrations reached 95 ppb. Both the spatial as well as the temporal variability of the simulated ozone concentrations were in good agreement with the measured values. The highest ozone values were found, in the southern zone, some 20 km downwind of the city center. It was found that about 32 ppb of fresh ozone are generated in the Grenoble plume. For developing ozone abatement strategies it is important to know whether in a specific area the ozone production is limited by VOC or NO x . Several indicators were proposed for distinguishing between VOC and NO x limitation. The morning Θ = τ HO VOC / τ HO NO x (the ratio of the lifetimes of OH against losses by reacting with VOC and NO x ) was applied and the afternoon indicator was κ =[H 2 O 2 ]/[HNO 3 ]. The Θ indicator gives information about the effect of changes in the emissions on the ozone formation in the air parcel which passes there, whereas κ provides information about the sensitivity of ozone formation in the aging plume. A combination of both indicators can be used to obtain a comprehensive view of the ozone formation in the Grenoble area. These results are confirmed by the investigation of the air mass regime with the time evolution of the ozone isopleths at the maximums locations (south and north west valleys).

Ozone Air Quality Modeling. A Case Study: A Heavily Vehicle Impacted Urban Avenue in Rio de Janeiro, Brazil

An empirical kinetic modeling approach is used in order to simulate ozone concentrations for an urban downtown area with high vehicular traffic. A base case was designed using experimental data for December 1999 in Presidente Vargas Avenue, Rio de Janeiro. The agreement between experimental and simulated results was quite good. The simulated ozone peak was obtained at 3:15 PM (23.0 ppb). A sensitivity-uncertainty analysis was performed and hypothetical scenarios were designed to illustrate the predictive potential of Air Quality Models.

Rural Highpoints from Other Journals

AIDS Care: HIV/AIDS‐Related Services for Women and the Rural Community Context by Castaneda, D.Teaching and Learning in Medicine: Interim Evaluation of the Rural Health Scholars Program by Lynch, DC, Teplin, SE, Willis, SE, Pathman, DE, Larsen, LC, Steiner, BD, & Bernstein, ID.Telemedicine Journal and e‐Health: Improved Rural Provider Access to Continuing Medical Education Through Interactive Videoconferencing by Callas, PW, Ricci, MA, & Caputo, MI.Journal of Air Waste Management Association: A Comparison of Measured and Simulated Ozone Concentrations in the Rural Areas of the Eastern United States during Summer 1995 by Sistla, G, Civerolo, K, Hao, W, & Rao, ST.

A Comparison of Measured and Simulated Ozone Concentrations in the Rural Areas of the Eastern United States during Summer 1995

ABSTRACT The recent regulatory actions toward a longer-term (i.e., 8-hr) average ozone standard have brought forth the potential for many rural areas in the eastern United States to be in noncompliance. However, since a majority of these rural areas have generally few sources of anthropogenic emissions, the measured ozone levels primarily reflect the effects of the transport of ozone and its precursor pollutants and natural emissions. While photochemical grid models have been applied to urban areas to develop ozone mitigation measures, these efforts have been limited to high ozone episode events only and do not adequately cover rural regions. In this study, we applied a photochemical modeling system, RAMS/UAM-V, to the eastern United States from June 1-August 31, 1995. The purpose of the study is to examine the predictive ability of the modeling system at rural monitoring stations that are part of the Clean Air Status Trends Network (CASTNet) and the Gaseous Pollutant Monitoring Program (GPMP). The results show that the measured daily 1-hr ozone maxima and the seasonal average of the daily 1-hr ozone maxima are in better agreement with the predictions of the modeling system than those for the daily 8-hr ozone maxima. Also, the response of the modeling system in reproducing the measured range of ozone levels over the diurnal cycle is poor, suggesting the need for improvement in the treatment of the physical and chemical processes of the modeling system during the nighttime and morning hours if it is to be used to address the 8-hr ozone standard.

Uncertainties in Episodic Ozone Modeling Stemming from Uncertainties in the Meteorological Fields

This paper examines the uncertainty associated with photochemical modeling using the Variable-Grid Urban Airshed Model (UAM-V) with two different prognostic meteorological models. The meteorological fields for ozone episodes that occurred during 17‐20 June, 12‐15 July, and 30 July‐2 August in the summer of 1995 were derived from two meteorological models, the Regional Atmospheric Modeling System (RAMS) and the Fifth-Generation Pennsylvania State University‐National Center for Atmospheric Research Mesoscale Model (MM5). The simulated ozone concentrations from the two photochemical modeling systems, namely, RAMS/ UAM-V and MM5/UAM-V, are compared with each other and with ozone observations from several monitoring sites in the eastern United States. The overall results indicate that neither modeling system performs significantly better than the other in reproducing the observed ozone concentrations. The results reveal that there is a significant variability, about 20% at the 95% level of confidence, in the modeled 1-h ozone concentration maxima from one modeling system to the other for a given episode. The model-to-model variability in the simulated ozone levels is for most part attributable to the unsystematic type of errors. The directionality for emission controls (i.e., NOx versus VOC sensitivity) is also evaluated with UAM-V using hypothetical emission reductions. The results reveal that not only the improvement in ozone but also the VOC-sensitive and NOx-sensitive regimes are influenced by the differences in the meteorological fields. Both modeling systems indicate that a large portion of the eastern United States is NOx limited, but there are model-to-model and episode-to-episode differences at individual grid cells regarding the efficacy of emission reductions.

Ozone Modeling Using Neural Networks

Abstract Ozone models for the city of Tulsa were developed using neural network modeling techniques. The neural models were developed using meteorological data from the Oklahoma Mesonet and ozone, nitric oxide, and nitrogen dioxide (NO2) data from Environmental Protection Agency monitoring sites in the Tulsa area. An initial model trained with only eight surface meteorological input variables and NO2 was able to simulate ozone concentrations with a correlation coefficient of 0.77. The trained model was then used to evaluate the sensitivity to the primary variables that affect ozone concentrations. The most important variables (NO2, temperature, solar radiation, and relative humidity) showed response curves with strong nonlinear codependencies. Incorporation of ozone concentrations from the previous 3 days into the model increased the correlation coefficient to 0.82. As expected, the ozone concentrations correlated best with the most recent (1-day previous) values. The model’s correlation coefficient was i...

Impact of biogenic emissions on ozone formation in the Mediterranean area – a BEMA modelling study

The aim of this modelling study is to understand and quantify the influence of biogenic volatile organic compound (BVOC) emissions on the formation of tropospheric ozone in the Burriana area (north of Valencia) on the east coast of Spain. The mesoscale modelling system used consists of the meteorology/transport module TVM and the chemical reaction mechanism RACM. The results of the model simulations are validated and compared with the data collected during the biogenic emissions in the mediterranean area (BEMA) field campaign that took place in June 1997. Anthropogenic and biogenic emission inventories have been constructed with an hourly resolution. Averaged (over the land area and over 24 h) emission fluxes for AVOC, anthropogenic NO x , BVOC and biogenic NO x are given by 16.0, 9.9, 6.2, and 0.7 kg km −2 day −1, respectively. The impact of biogenic emissions is investigated on peak ozone values by performing simulations with and without biogenic emissions, while keeping anthropogenic emissions constant. The impact on ozone formation is also studied in combination with some anthropogenic emissions reduction strategies, i.e. when anthropogenic VOC emissions and/or NO x emissions are reduced. A factor separation technique is applied to isolate the impact due to biogenic emissions from the overall impact due to biogenic and anthropogenic emissions together. The results indicate that the maximum impact of biogenic emissions on ozone formation represents at the most 10 ppb, while maximum ozone values are of the order of 100 ppb. At different locations the maximum impact is reached at different times of the day depending on the arrival time of the sea breeze. It is also shown that this impact does not coincide in time with the maximum simulated ozone concentrations that are reached over the day. By performing different emission reduction scenarios, BVOC impacts are found to be sensitive mainly to NO x , and not to AVOC. Finally, it is shown that amongst the various BVOCs emitted by the citrus plantations in Burriana, the carbonyl species contribute the most to ozone formation.

Simulation of Air Pollution from Mobile Source Emissions in the City of Rio de Janeiro

A simple trajectory model and the chemical mechanism, including the chemistry of ethanol and methyl-tert-butyl ether (MTBE), were used to simulate ozone concentrations at Avenida Brasil, a busy expressway in the city of Rio de Janeiro where emissions from mobile sources are considered to be the major source of air pollution. The calculated ozone maximum of 22.4 ppb at 14:57 h is in good agreement with experimental measurements. Ozone isopleth diagrams were calculated based on the meteorological and emission scenario of that expressway, showing that ozone concentrations in Rio de Janeiro are a consequence of the high levels of NOx .