Chemical Transport Simulations Research Articles

Chemical Transport Reactions and Simulation of the Behavior of Various Ceramics in the T-11M Tokamak with Experimental Confirmation on Electrical Porcelain

Chemical Transport Reactions and Simulation of the Behavior of Various Ceramics in the T-11M Tokamak with Experimental Confirmation on Electrical Porcelain

Estimating nitrogen and sulfur deposition across China during 2005 to 2020 based on multiple statistical models

Abstract. Due to the rapid development of industrialization and a substantial economy, China has become one of the global hotspots of nitrogen (N) and sulfur (S) deposition following Europe and the USA. Here, we developed a dataset with full coverage of N and S deposition from 2005 to 2020, with multiple statistical models that combine ground-level observations, chemistry transport simulations, satellite-derived vertical columns, and meteorological and geographic variables. Based on the newly developed random forest method, the multi-year averages of dry deposition of oxidized nitrogen (OXN), reduced nitrogen (RDN), and S in China were estimated at 10.4, 14.4, and 16.7 kg N/S ha−1 yr−1, and the analogous numbers for total deposition were respectively 15.2, 20.2, and 25.9 kg N/S ha−1 yr−1 when wet deposition estimated previously with a generalized additive model (GAM) was included. The dry to wet deposition ratio (Rdry/wet) of N stabilized in earlier years and then gradually increased especially for RDN, while that of S declined for over 10 years and then slightly increased. The RDN to OXN deposition ratio (RRDN/OXN) was estimated to be larger than 1 for the whole research period and clearly larger than that of the USA and Europe, with a continuous decline from 2005 to 2011 and a more prominent rebound afterwards. Compared with the USA and Europe, a more prominent lagging response of OXN and S deposition to precursor emission abatement was found in China. The OXN dry deposition presented a descending gradient from east to west, while the S dry deposition a descending gradient from north to south. After 2012, the OXN and S deposition in eastern China declined faster than the west, attributable to stricter emission controls. Positive correlation was found between regional deposition and emissions, while smaller deposition to emission ratios (D/E) existed in developed eastern China, attributed to more intensive human activities and thereby anthropogenic emissions.

Nonagricultural emissions enhance dimethylamine and modulate urban atmospheric nucleation

Gas-phase dimethylamine (DMA) has recently been identified as one of the most important vapors to initiate new particle formation (NPF), even in China’s polluted atmosphere. Nevertheless, there remains a fundamental need for understanding the atmospheric life cycle of DMA, particularly in urban areas. Here we pioneered large-scale mobile observations of the DMA concentrations within cities and across two pan-region transects of north-to-south (∼700 km) and west-to-east (∼2000 km) in China. Unexpectedly, DMA concentrations (mean ± 1σ) in South China with scattered croplands (0.018 ± 0.010 ppbv, 1 ppbv=10−9 L/L) were over three times higher than those in the north with contiguous croplands (0.005 ± 0.001 ppbv), suggesting that nonagricultural activities may be an important source of DMA. Particularly in non-rural regions, incidental pulsed industrial emissions led to some of the highest DMA concentration levels in the world (>2.3 ppbv). Besides, in highly urbanized areas of Shanghai, supported by direct source-emission measurements, the spatial pattern of DMA was generally correlated with population (R2 = 0.31) due to associated residential emissions rather than vehicular emissions. Chemical transport simulations further show that in the most populated regions of Shanghai, residential DMA emissions can contribute for up to 78% of particle number concentrations. Shanghai is a case study for populous megacities, and the impacts of nonagricultural emissions on local DMA concentration and nucleation are likely similar for other major urban regions globally.

LNOx Emission Model for Air Quality and Climate Studies Using Satellite Lightning Mapper Observations

AbstractA lightning nitrogen oxides (LNOx) emissions model using satellite‐observed lightning optical energy is introduced for utilization in Air Quality modeling systems. The effort supports assessments of air‐quality/climate coupling as related to the influence of LNOx on atmospheric chemistry. The Geostationary Lightning Mapper (GLM), International Space Station Lightning Imaging Sensor (ISS‐LIS), and the Tropical Rainfall Measuring Mission (TRMM) LIS data are used to examine the efficacy of the method, extend the previously derived LNOx record, and demonstrate a path for using ISS‐LIS observations to cross‐calibrate regional LNOx estimates from the future global constellation of geostationary lightning observations. A detailed evaluation of the GLM data set is provided to establish the robustness of observations for LNOx estimates and to make preliminary assessments of the LNOx emissions model. Seasonal and geographical variation, land/ocean contrast, and annual fluctuation in the GLM observed lightning activity and flash optical energy are provided. GLM detection substantially degrades with the increase in the field of view, resulting in 44% more flashes and 40% less optical energy observation by GLM‐16 (compared to GLM‐17) to the east of the middle‐longitude between the two mappers (106.2°W). Regular horizontal striations are found in the optical energy product. On average, GLM flashes matched to the cloud‐to‐ground flashes have ∼30% longer duration, 50%–70% more extension, and ≥100% higher optical energy compared to the unmatched flashes (assumed to be intra‐cloud). The results from summer‐long chemical transport simulations using LNOx generated from the emission model agrees with previous studies and shows consistency across the GLM/LIS data sets.

Meteorological export and deposition fluxes of black carbon on glaciers of the central Chilean Andes

Abstract. Air pollution in the central zone of Chile is not only a public health concern but also threatens water resources and climate, in connection with the transport and deposition of black carbon (BC) from urban centers onto the glaciers of the Andes. Chemistry-transport simulations reveal a seasonal dichotomy in the flux and latitudinal pattern of BC deposition on glaciers of the central Chilean Andes. The average deposition flux of BC on glaciers between 30 and 37∘ S is 4 times larger in winter, affecting mostly low-elevation glaciers, whereas the smaller summertime flux affects glaciers evenly, irrespective of their elevation. The contribution of emissions from the city of Santiago is dominant in summertime with more than 50 % along the Andes but minor in wintertime with less than 20 % even close to the capital city. Transport at larger scales and more local sources likely account for the remaining flux. The superimposition of synoptic-scale circulation and local mountain-valley circulation along the Andes drives the differences between summertime and wintertime deposition fluxes and generates a greater meteorological export potential during summer months. Future emissions and climate projections suggest that under the RCP8.5 scenario the gap between summertime and wintertime BC export and deposition flux could decrease, thereby pointing to summertime emission control gaining relevance. The chemistry-transport modeling approach for BC deposition on the Andes sheds light on the importance of the often disregarded summertime emissions on the radiative balance of its glaciers, particularly in the vicinity of Santiago.

UrbanChemFoam 1.0: large-eddy simulation of non-stationary chemical transport of traffic emissions in an idealized street canyon

Abstract. This paper describes a large-eddy simulation based chemical transport model, developed under the OpenFOAM framework, implemented to simulate dispersion and chemical transformation of nitrogen oxides from traffic sources in an idealized street canyon. The dynamics of the model, in terms of mean velocity and turbulent fluctuation, are evaluated using available stationary measurements. A transient model run using a photostationary reaction mechanism for nitrogen oxides and ozone subsequently follows, where non-stationary conditions for meteorology, background concentrations, and traffic emissions are applied over a 24 h period, using regional model data and measurements obtained for the city of Berlin in July 2014. Diurnal variations of pollutant concentrations indicate dependence on emission levels, background concentrations, and solar state. Comparison of vertical and horizontal profiles with corresponding stationary model runs at select times show that while there are only slight differences in velocity magnitude, visible changes in primary and secondary flow structures can be observed. In addition, temporal variations in diurnal profile and cumulative species concentration result in significant deviations in computed pollutant concentrations between transient and stationary model runs.

Health Benefits and Costs of Clean Heating Renovation: An Integrated Assessment in a Major Chinese City.

China has been promoting one of the world's largest campaigns for clean heating renovation since 2017. Here, we present an integrated cost-benefit analysis in a major prefecture-level city by combining a large-scale household energy survey and PM2.5 exposure measurement, high-resolution chemical transport simulation, and health impact assessment. We find that the completed renovation decreases the share of solid fuels in the heating energy mix from 96 to 6% and achieves a concomitant reduction of cooking solid-fuel use by 70%. The completed renovation decreases the ambient PM2.5 concentration in Linfen by 0.5-5 μg m-3 (2.4 μg m-3 on average) and decreases the integrated PM2.5 exposure by 4.2 (3.5-5.0) μg m-3. The renovation is estimated to avoid 162 (125-225) and 328 (254-457) premature deaths annually based on two health impact assessment methods. The ratios of monetized health benefits to cost are 1.51 (0.73-2.59) and 3.06 (1.49-5.23) based on the above two methods. The benefit-to-cost ratio is projected to remain high if the renovation is further expanded. More polluted and less wealthy households enjoy larger health benefits but also experience a higher expense increase, suggesting that a more carefully designed subsidy policy is needed to protect low-income households.

Impact of Urban Pollution on Organic-Mediated New-Particle Formation and Particle Number Concentration in the Amazon Rainforest.

A major challenge in assessing the impact of aerosols on climate change is to understand how human activities change aerosol loading and properties relative to the pristine/preindustrial baseline. Here, we combine chemical transport simulations and field measurements to investigate the effect of anthropogenic pollution from an isolated metropolis on the particle number concentration over the preindustrial-like Amazon rainforest through various new-particle formation (NPF) mechanisms and primary particle emissions. To represent organic-mediated NPF, we employ a state-of-the-art model that systematically simulates the formation chemistry and thermodynamics of extremely low volatility organic compounds, as well as their roles in NPF processes, and further update the model to improve organic NPF simulations under human-influenced conditions. Results show that urban pollution from the metropolis increases the particle number concentration by a factor of 5-25 over the downwind region (within 200 km from the city center) compared to background conditions. Our model indicates that NPF contributes over 70% of the total particle number in the downwind region except immediately adjacent to the sources. Among different NPF mechanisms, the ternary NPF involving organics and sulfuric acid overwhelmingly dominates. The improved understanding of particle formation mechanisms will help better quantify anthropogenic aerosol forcing from preindustrial times to the present day.

Simulation of water and chemical transport of chloride from the forest ecosystem to the stream

The study evaluates the biogeochemical model ForSAFE-2D, designed to simulate water and chemical transport from the forest to the stream, by simulating the hydrology and the transport of the chemical tracer chloride (Cl−) along a forest hillslope in Northern Sweden. The simulated Cl− exports were in balance with the simulated inputs but measurements suggested a net release of Cl− from the catchment. Underestimated deposition inputs (deposition peaks and possibly dry deposition) were probably and partially responsible for this mismatch. However, we could not exclude that other soil biogeochemical processes omitted in ForSAFE-2D could also contribute to Cl− exports from the catchment. The study showed that ForSAFE-2D is a promising tool to better understand the factors that regulate the chemical export from the forest to the stream. The results also confirmed that there are limitations in using Cl− as a tracer in forest ecosystems.

Monitorización de las concentraciones atmosféricas de metano y óxido nitroso a partir del Metop/IASI

<p>Future of the Earth-atmosphere system will depend, to a large extent, on our capability of understanding all the processes driving climate change and, in this context, of outstanding importance are the monitoring and the investigation of greenhouse gases (GHGs), as main drivers of the Earth’s climate change. With this idea the project INMENSE (IASI for Surveying Methane and Nitrous Oxide in the Troposphere) was born, which aims to improve our current understanding of the atmospheric budgets of two of the most important well-mixed greenhouse gases, methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O). To this end, INMENSE has generated a new global observational data set of middle/upper tropospheric concentrations of CH<sub>4</sub> and N<sub>2</sub>O from the space-based remote sensor IASI (Infrared Atmospheric Sounding Interferometer), on board the meteorological satellites EUMETSAT/Metop. In this work the INMENSE IASI CH<sub>4</sub> and N<sub>2</sub>O products are presented, characterized and comprehensively validated by using a multiplatform reference database (aircraft vertical profiles, ground-based in-situ and remote-sensing observations). This extensive validation exercise suggests that the IASI CH<sub>4</sub> and N<sub>2</sub>O products shows a precision between 1-3% and a bias of 2% as well as they are consistent temporally and spatially. Finally, the CH<sub>4 </sub>and N<sub>2</sub>O IASI observations over the Iberian Peninsula have been compared to MOCAGE chemical transport simulations, assessing the degree of agreement between both datasets.</p><p> </p>

Оценка масштабируемости программы расчета движения примесей в атмосфере средствами симулятора gem5

В данной работе мы предлагаем новую эффективную программную реализацию алгоритма расчета трансконтинентального переноса примеси в атмосфере от естественного или антропогенного источника на адаптивной конечно-разностной сетке, концентрирующей свои узлы внутри переносимого облака примеси, где наблюдаются резкие изменения значений ее массовой доли, и максимально разрежающей узлы во всех остальных частях атмосферы, что позволяет минимизировать общее количество узлов. Особенностью реализации является представление адаптивной сетки в виде комбинации динамических (дерево, связный список) и статических (массив) структур данных. Такое представление сетки позволяет увеличить скорость выполнения расчетов в два раза по сравнению со стандартным подходом представления адаптивной сетки только через динамические структуры данных.

The challenge of simulating the sensitivity of the Amazonian cloud microstructure to cloud condensation nuclei number concentrations

Abstract. The realistic representation of aerosol–cloud interactions is of primary importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions in the Amazon region has been one of the motivations for several field campaigns, including the airborne “Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA)” campaign based in Manaus, Brazil, in September 2014. In this work we combine in situ and remotely sensed aerosol, cloud, and atmospheric radiation data collected during ACRIDICON-CHUVA with regional, online-coupled chemistry-transport simulations to evaluate the model's ability to represent the indirect effects of biomass burning aerosol on cloud microphysical and optical properties (droplet number concentration and effective radius). We found agreement between the modeled and observed median cloud droplet number concentration (CDNC) for low values of CDNC, i.e., low levels of pollution. In general, a linear relationship between modeled and observed CDNC with a slope of 0.3 was found, which implies a systematic underestimation of modeled CDNC when compared to measurements. Variability in cloud condensation nuclei (CCN) number concentrations was also underestimated, and cloud droplet effective radii (reff) were overestimated by the model. Modeled effective radius profiles began to saturate around 500 CCN cm−3 at cloud base, indicating an upper limit for the model sensitivity well below CCN concentrations reached during the burning season in the Amazon Basin. Additional CCN emitted from local fires did not cause a notable change in modeled cloud droplet effective radii. Finally, we also evaluate a parameterization of CDNC at cloud base using more readily available cloud microphysical properties, showing that we are able to derive CDNC at cloud base from cloud-side remote-sensing observations.

Direct Radiative Effect and Public Health Implications of Aerosol Emissions Associated with Shifting to Gasoline Direct Injection (GDI) Technologies in Light-Duty Vehicles in the United States.

Due to their enhanced fuel economy, the market share of gasoline direct injection (GDI) vehicles has increased significantly over the past decade. However, GDI engines emit higher levels of black carbon (BC) aerosols compared to traditional port fuel injection (PFI) engines. Here, we performed coupled chemical transport and radiative transfer simulations to estimate the aerosol-induced public health and direct radiative effects of shifting the U.S. fleet from PFI to GDI technology. By comparing simulations with current emission profiles and emission profiles modified to reflect a shift from PFI to GDI, we calculated the change in aerosol (mostly BC) concentrations associated with the fleet change. Standard concentration-response calculations indicated that the total annual deaths in the U.S. attributed to particulate gasoline-vehicle emissions would increase from 855 to 1599 due to shifting from PFI to GDI. Furthermore, the increase in BC associated with the shift would lead to an annual average positive radiative effect over the U.S. of approximately +0.075 W/m2, with values as large as +0.45 W/m2 over urban regions. On the other hand, the reduction in CO2 emissions associated with the enhanced fuel economy of GDI vehicles would yield a globally uniform negative radiative effect, estimated to be -0.013 W/m2 over a 20 year time horizon. Therefore, the climate burden of the increase in BC emissions dominates over the U.S., especially over source regions.

Evaluation of NASA's high-resolution global composition simulations: Understanding a pollution event in the Chesapeake Bay during the summer 2017 OWLETS campaign

Recirculation of pollutants due to a bay breeze effect is a key meteorological mechanism impacting air quality near urban coastal areas, but regional and global chemical transport models have historically struggled to capture this phenomenon. We present a case study of a high ozone (O3) episode observed over the Chesapeake Bay during the NASA Ozone Water-Land Environmental Transition Study (OWLETS) in summer 2017. OWLETS included a complementary suite of ground-based and airborne observations, with which we characterize the meteorological and chemical context of this event and develop a framework to evaluate model performance. Two publicly-available NASA global high-resolution coupled chemistry-meteorology models (CCMMs) are investigated: GEOS-CF and MERRA2-GMI. The GEOS-CF R2 value for comparisons between the NASA Sherpa C-23 aircraft measurements to the GEOS-CF resulted in good agreement (R2: 0.67) on July 19th and fair agreement (R2: 0.55) for July 20th. Compared to surface observations, we find the GEOS-CF product with a 25 × 25 km2 grid box, at an hourly (R2: 0.62 to 0.87) and 15-min (R2: 0.64 to 0.87) interval for six regional sites outperforms the hourly nominally 50 × 50 km2 gridded MERRA2-GMI (R2: 0.53 to 0.76) for four of the six sites, suggesting it is better capable of simulating complex chemical and meteorological features associated with ozone transport within the Chesapeake Bay airshed. When the GEOS-CF product was compared to the TOLNet LiDAR observations at both NASA Langley Research Center (LaRC) and the Chesapeake Bay Bridge Tunnel (CBBT), the median differences at LaRC were −6 to 8% and at CBBT were ±7% between 400 and 2000 m ASL. This indicates that, for this case study, the GEOS-CF is able to simulate surface level ozone diurnal cycles and vertical ozone profiles at small scales between the surface level and 2000 m ASL. Evaluating global chemical model simulations at sub-regional scales will help air quality scientists understand the complex processes occurring at small spatial and temporal scales within complex surface terrain changes, simulating nighttime chemistry and deposition, and the potential to use global chemical transport simulations in support of regional and sub-regional field campaigns.

Simulation of Chemical Transport by Typhoon Mireille (1991)

AbstractThis study examines the transport of chemical species to the upper troposphere/lower stratosphere (UTLS) by Typhoon Mireille (1991). We follow an integrated research approach, using in situ flight data when available and results from a high‐resolution chemical transport model. The Weather Research and Forecasting model coupled with chemistry (WRF‐Chem) was used with an innermost grid spacing of 3 km to explicitly resolve the convection being studied. Mireille was well simulated based on comparisons between the simulated fields and in situ chemical measurements from NASA's Pacific Exploratory Mission‐West A field project. Results from the simulated fields show that pollution from distant sources is ingested by Mireille and subsequently lofted by eyewall convection to the upper troposphere, enhancing concentrations in this region. Flux calculations suggest that a strong tropical cyclone (TC), such as Mireille, can impact UTLS chemistry as much as a continental middle‐latitude cyclone. Furthermore, overshooting convective cells in Mireille produced values of chemical flux density at tropopause level that are as much as 15–30 times greater than that of theTC as a whole. Although overshooting tops comprise only a small area of the simulated total TC, they transport large quantities of gaseous species to the upper troposphere because of their strong updrafts.

Air Quality and Health Cobenefits of Different Deep Decarbonization Pathways in California.

As the world's fifth-largest economy, California has committed to reduce its greenhouse gas (GHG) emissions by 80% below 1990 levels by 2050. While previous studies have shown that GHG reductions could synergistically decrease air pollutant emissions and protect public health, limited research has been conducted to compare the health cobenefits of different technology pathways toward deep decarbonization. Using an integrated approach that combines energy and emission technology modeling, high-resolution chemical transport simulation, and health impact assessment, we find that achievement of the 80% GHG reduction target would bring substantial air quality and health cobenefits. The cobenefits, however, highly depend on the selected technology pathway largely because of California's relatively clean energy structure. Compared with the business-as-usual levels, a decarbonization pathway that focuses on electrification and clean renewable energy is estimated to reduce concentrations of fine particulate matter (PM2.5) by 18-37% in major metropolitan areas of California and subsequently avoid about 12 100 (9600-14 600) premature deaths. In contrast, only a quarter of such health cobenefits, i.e., 2800 (2300-3400) avoided deaths, can be achieved through a pathway focusing more on combustible renewable fuels. After subtracting the cost, the net monetized benefit of the electrification-focused pathway still exceeds that of the renewable fuel-focused pathway, indicating that a cleaner but more expensive decarbonization pathway may be more preferable in California.

The Ozone Water-Land Environmental Transition Study (OWLETS): An Innovative Strategy for Understanding Chesapeake Bay Pollution Events.

Coastal regions have historically represented a significant challenge for air quality investigations due to water-land boundary transition characteristics and a paucity of measurements available over water. Prior studies have identified the formation of high levels of ozone over water bodies, such as the Chesapeake Bay, that can potentially recirculate back over land to significantly impact populated areas. Earth-observing satellites and forecast models face challenges in capturing the coastal transition zone where small-scale meteorological dynamics are complex and large changes in pollutants can occur on very short spatial and temporal scales. An observation strategy is presented to synchronously measure pollutants 'over-land' and 'over-water' to provide a more complete picture of chemical gradients across coastal boundaries for both the needs of state and local environmental management and new remote sensing platforms. Intensive vertical profile information from ozone lidar systems and ozonesondes, obtained at two main sites, one over land and the other over water, are complemented by remote sensing and in-situ observations of air quality from ground-based, airborne (both personned and unpersonned), and shipborne platforms. These observations, coupled with reliable chemical transport simulations, such as the NOAA National Air Quality Forecast Capability (NAQFC), are expected to lead to a more fully characterized and complete land-water interaction observing system that can be used to assess future geostationary air quality instruments, such as the NASA Tropospheric Emissions: Monitoring of Pollution (TEMPO) as well as current low earth orbiting satellites, such as the European Space Agency's Sentinel 5-Precursor (S5-P) with its Tropospheric Monitoring Instrument (TROPOMI).

Change in household fuels dominates the decrease in PM2.5 exposure and premature mortality in China in 2005–2015

To tackle the severe fine particle (PM2.5) pollution in China, the government has implemented stringent control policies mainly on power plants, industry, and transportation since 2005, but estimates of the effectiveness of the policy and the temporal trends in health impacts are subject to large uncertainties. By adopting an integrated approach that combines chemical transport simulation, ambient/household exposure evaluation, and health-impact assessment, we find that the integrated population-weighted exposure to PM2.5 (IPWE) decreased by 47% (95% confidence interval, 37-55%) from 2005 [180 (146-219) μg/m3] to 2015 [96 (83-111) μg/m3]. Unexpectedly, 90% (86-93%) of such reduction is attributed to reduced household solid-fuel use, primarily resulting from rapid urbanization and improved incomes rather than specific control policies. The IPWE due to household fuels for both cooking and heating decreased, but the impact of cooking is significantly larger. The reduced household-related IPWE is estimated to avoid 0.40 (0.25-0.57) million premature deaths annually, accounting for 33% of the PM2.5-induced mortality in 2015. The IPWE would be further reduced by 63% (57-68%) if the remaining household solid fuels were replaced by clean fuels, which would avoid an additional 0.51 (0.40-0.64) million premature deaths. Such a transition to clean fuels, especially for heating, requires technology innovation and policy support to overcome the barriers of high cost of distribution systems, as is recently being attempted in the Beijing-Tianjin-Hebei area. We suggest that household-fuel use be more highly prioritized in national control policies, considering its effects on PM2.5 exposures.

Use of Fine-Resolution AOD-Derived Long-Term PM2.5 Concentrations to Characterize Adverse Health Outcomes

Remote sensing data from satellites, which can be combined with land use, meteorology, and chemical transport simulations, and trained at monitoring locations, have some distinct advantages over monitoring data in assessing health effects of air pollution. Compared to monitoring data, they can provide fine scale spatial resolution and access to populations not living near monitors; compared to land use regression they can provide fine scale temporal resolution; and compared to inexpensive monitors they can provide better accuracy and historical estimates going back over a decade. I discuss several such models, their performance, and demonstrate how they perform in different studies compared to monitors. In the VIVA birth cohort, an IQR increase in modeled PM2.5 had a stronger association between Impaired Glucose Tolerance (OR=1.64 (1.11, 2.42)) compared to monitored PM2.5 (OR=1.34 (0.98, 1.84)). In the Medicare Mortality cohort they provide somewhat stronger associations between mortality and PM2.5, but much stronger associations with ozone HR= 1.011 (1.010–1.012) Vs 1.001 (1.000–1.002) for 10 ppb. In the New Jersey mortality data they allow differences in differences approach within census tracts that would not be feasible with monitors.

Application and evaluation of two model fusion approaches to obtain ambient air pollutant concentrations at a fine spatial resolution (250m) in Atlanta

Epidemiologic studies rely on accurately characterizing spatiotemporal variation in air pollutant concentrations. This work presents two model fusion approaches that use publicly available chemical transport simulations, dispersion model simulations, and observations to estimate air pollutant concentrations at a neighborhood-level spatial resolution while incorporating comprehensive chemistry and emissions sources. The first method is additive and the alternative method is multiplicative. These approaches are applied to Atlanta, GA at a 250 m grid resolution to obtain daily 24-hr averaged PM2.5 and 1-hr max CO and NOx concentrations during the years 2003–2008 for use in health studies. The modeled concentrations provide comprehensive estimates with steep spatial gradients near roadways, secondary formation and loss, and effects of regional sources that can influence daily variation in ambient pollutant concentrations. Results show high temporal and spatial correlation and low biases across monitors, providing accurate pollutant concentration estimates for epidemiologic analyses.