Sharon Phillips

Modeling intercontinental air pollution transport over the trans‐Pacific region in 2001 using the Community Multiscale Air Quality modeling system

[1] The Community Multiscale Air Quality modeling system is used to study the intercontinental transport of air pollution across the Pacific region. Baseline simulations are conducted for January, April, July, and October 2001 at a 108 km horizontal grid resolution. A sensitivity simulation is conducted for April 2001 to study the impact of Asian anthropogenic emissions on the United States’s air quality. Process analysis is conducted to study pollutant formation and transport and to quantify the relative contributions of atmospheric processes to ozone (O3) and fine particulate matter (PM2.5). Model simulations are evaluated with available surface, aircraft, and satellite observations. Simulated meteorology basically captures the synoptic pattern, but precipitation amounts are significantly underpredicted. Most of the PM2.5 components are overestimated over the United States and most gases are underestimated over east Asia. Simulated NO2 and CO columns agree well with satellite observations. Aerosol optical depths and tropospheric O3 residuals are underpredicted, especially in July. The simulated horizontal fluxes and process analyses show that the transport in the lower free troposphere followed by a large-scale subsidence over the United States provides a major Asian pollution export pathway for most pollutants, while the transport in the planetary boundary layer also plays an important role, especially for CO, O3 ,P M2.5, and SO4� . The background concentrations of O3 and SO4� in the western United States can increase by � 1 ppb (� 2.5%) and 0.4 m gm � 3 (� 20%) in monthly average, up to 2.5 ppb and 1.0 m gm � 3 in daily average, respectively, due to the Asian emissions in April.

The geographic distribution and economic value of climate change-related ozone health impacts in the United States in 2030

In this United States-focused analysis we use outputs from two general circulation models (GCMs) driven by different greenhouse gas forcing scenarios as inputs to regional climate and chemical transport models to investigate potential changes in near-term U.S. air quality due to climate change. We conduct multiyear simulations to account for interannual variability and characterize the near-term influence of a changing climate on tropospheric ozone-related health impacts near the year 2030, which is a policy-relevant time frame that is subject to fewer uncertainties than other approaches employed in the literature. We adopt a 2030 emissions inventory that accounts for fully implementing anthropogenic emissions controls required by federal, state, and/or local policies, which is projected to strongly influence future ozone levels. We quantify a comprehensive suite of ozone-related mortality and morbidity impacts including emergency department visits, hospital admissions, acute respiratory symptoms, and lost school days, and estimate the economic value of these impacts. Both GCMs project average daily maximum temperature to increase by 1–4°C and 1–5 ppb increases in daily 8-hr maximum ozone at 2030, though each climate scenario produces ozone levels that vary greatly over space and time. We estimate tens to thousands of additional ozone-related premature deaths and illnesses per year for these two scenarios and calculate an economic burden of these health outcomes of hundreds of millions to tens of billions of U.S. dollars (2010

Modelling and analysis of the atmospheric nitrogen deposition in North Carolina

). Implications: Near-term changes to the climate have the potential to greatly affect ground-level ozone. Using a 2030 emission inventory with regional climate fields downscaled from two general circulation models, we project mean temperature increases of 1 to 4°C and climate-driven mean daily 8-hr maximum ozone increases of 1–5 ppb, though each climate scenario produces ozone levels that vary significantly over space and time. These increased ozone levels are estimated to result in tens to thousands of ozone-related premature deaths and illnesses per year and an economic burden of hundreds of millions to tens of billions of U.S. dollars (2010

Considering ecological formulations for estimating deposition velocity in air quality models

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Sensitivity of Ambient Atmospheric Formaldehyde and Ozone to Precursor Species and Source Types Across the United States

The United States Environmental Protection Agencys Community Multiscale Air Quality (CMAQ) regional-scale model is used to study concentrations and dry deposition of nitrogen species in North Carolina (NC) during the summer season. Each modelled and measured species featured a similar diurnal trend. A process budget analysis (production and removal evaluation) of NO, NO2, and NOY depicted the models capability to evaluate various process contributions. Dry deposition of NH3 contributed 34.2 ± 57.9 µg N m-2 hr-1; whereas HNO3 contributed slightly larger dry deposition of nitrogen, 35.2 ± 16.0 µg N m-2 hr-1, in NC. NH4+ and NO3- hourly-averaged wet deposition fluxes were calculated as 37.3 ± 19.7 µg N -2 hr-1 and 40.6 ± 11.8 µg N m-2 hr-1, respectively. Examination of total nitrogen deposition during the summer season in NC found that NH3 contributes approximately 50% of the dry deposition and NO3- contributes approximately 50% of the wet deposition.

Mobile source contributions to ambient ozone and particulate matter in 2025

A dry deposition modelling approach that includes surface feedback through photosynthesis relationships was recently developed. A canopy photosynthesis model is dynamically coupled to an atmospheric model with prognostic soil hydrology and surface energy balance. The effective surface resistance is calculated for a realistic and fully interactive estimation of gaseous deposition velocity (Vd). The model was able to correctly estimate observed ozone Vd over agricultural fields. The same model was tested for its ability to simulate ammonia Vd near an animal agricultural facility. The scheme did not reproduce the bi-directional exchange and had a much smaller range as compared to observations. The model was modified to include a simple ammonia compensation point formulation and the results were much closer to the observations. Study concludes that ecological approaches with default parameterisation and biophysical constants are convenient and effective in estimating Vd for air quality models.

Compilation and interpretation of photochemical model performance statistics published between 2006 and 2012

Formaldehyde (HCHO) is an important air pollutant from both an atmospheric chemistry and human health standpoint. This study uses an instrumented photochemical Air Quality Model, CMAQ-DDM, to identify the sensitivity of HCHO concentrations across the United States (U.S.) to major source types and hydrocarbon speciation. In July, biogenic sources of hydrocarbons contribute the most (92% of total hydrocarbon sensitivity), split between isoprene and other alkenes. Among anthropogenic sources, mobile sources of hydrocarbons and nitrogen oxides (NO x) dominate. In January, HCHO is more sensitive to anthropogenic hydrocarbons than biogenic sources, especially mobile sources and residential wood combustion (36% of national hydrocarbon sensitivity). While ozone (O3) is three times more sensitive to NO x than hydrocarbons across most areas of the U.S., HCHO is six times more sensitive to hydrocarbons than NO x, largely due to sensitivity to biogenic precursors and the importance of low-NO x chemistry. In winter, both HCHO and O3 show negative sensitivity to NO x (increases with the removal of NO x), although O3 increases are larger. Relative sensitivities do not change substantially across different regions of the country.

Assessment of air quality benefits from national air pollution control policies in China. Part II: Evaluation of air quality predictions and air quality benefits assessment

The contribution of precursor emissions from 17 mobile source sectors to ambient ozone and fine particulate matter levels across the U.S. were evaluated, using the CAMx photochemical model, to identify which mobile source sectors are projected to have the largest impacts on air pollution in 2025. Both onroad and nonroad sectors contribute considerably to projected air pollution across much of the country. Summer ozone season ozone contributions between 2 and 5 ppb, which are among the highest levels presented on the maps of mobile source sectors, are largely found in the southeast United States from the onroad sectors, most notably light-duty and heavy-duty vehicles, and along the coastline from the Category 3 (C3) marine sector. Annual average PM2.5 contributions between 0.5 to 0.9 μg/m3, which are among the highest levels presented on the maps of mobile source sectors, are found throughout the Midwest and along portions of the east and west coast from onroad sectors as well as nonroad diesel and rail sectors. Additionally, contributions of precursor emissions to ambient ozone and PM2.5 levels were evaluated to understand the range of impacts from precursors in the various mobile source sectors. For most mobile source sectors, in most locations, NOX emissions contributed more to ozone than VOC emissions, and secondary PM2.5 contributed more to ambient PM2.5 than primary PM2.5. The largest ozone levels on the maps showing contributions from mobile source NOX emissions tended to be between 2 and 5 ppb, while the largest ozone levels on the maps showing contributions from mobile source VOC emissions tended to be between 0.9 and 2 ppb, except for southern California where ozone contributions from VOC emissions from onroad light duty vehicles were between 2 and 5 ppb. The largest contributions to ambient PM2.5 on the maps showing primary and secondary contributions from mobile source sectors tended to be between 0.1 and 0.5 μg/m3. The contribution from primary PM2.5 extended over localized areas (urban-scale) and the contribution from secondary PM2.5 extended over more regional (multi-state) areas.