Future year (2028) source apportionment modeling to support Regional Haze Rule planning in the western U.S.

The Western Regional Air Partnership (WRAP) has developed a modeling platform to simulate the formation of haze-causing particles that impact federally-protected lands in the western United States. To assist state air quality planners in determining which emission sources are likely candidates for future mitigation, several source apportionment scenarios were evaluated, and two sets of results for the year 2028 are presented here: 1) a "high-level important regional sources" version, with broad emission categories (i.e.

Assessment of progress toward regional haze rule visibility goals using United States anthropogenic emissions rate of progress.

The U.S. EPA developed the Regional Haze Rule to address Section 7491 of the 1977 Clean Air Act Amendments to prevent any future and remedy any existing visibility impairment due to manmade air pollution at Federal Class I areas (CIAs).

Changes in Ozone Chemical Sensitivity in the United States from 2007 to 2016.

Anthropogenic nitrogen oxide (NO) and volatile organic compound (VOC) emissions in the U.S. have declined substantially over the last decade, altering the NO-VOC chemistry and ozone (O) production characteristics of many areas.

Scientific assessment of background ozone over the U.S.: Implications for air quality management.

Ozone (O) is a key air pollutant that is produced from precursor emissions and has adverse impacts on human health and ecosystems. In the U.S.

Air pollutant source characterization using the revised regional haze tracking metric and a photochemical grid model and implications for regional haze planning.

The 2017 revisions to the Regional Haze Rule clarify that visibility progress at Class I national parks and wilderness areas should be tracked on days with the highest anthropogenic contributions to haze (impairment). We compare the natural and anthropogenic contributions to haze in the western United States in 2011 estimated using the Environmental Protection Agency (EPA) recommended method and using model projections from the Comprehensive Air Quality Model with Extensions (CAMx) and the Particulate Source Apportionment Tool (PSAT). We do so because these two methods will be used by states to demonstrate visibility progress by 2028.

Modeling NHNO Over the San Joaquin Valley During the 2013 DISCOVER-AQ Campaign.

The San Joaquin Valley (SJV) of California experiences high concentrations of particulate matter NHNO during episodes of meteorological stagnation in winter. A rich data set of observations related to NHNO formation was acquired during multiple periods of elevated NHNO during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign in SJV in January and February 2013. Here NHNO is simulated during the SJV DISCOVER-AQ study period with the Community Multiscale Air Quality (CMAQ) model, diagnostic model evaluation is performed using the DISCOVER-AQ data set, and integrated reaction rate analysis is used to quantify HNO production rates.

Evaluation of the Community Multiscale Air Quality Model for Simulating Winter Ozone Formation in the Uinta Basin.

The Weather Research and Forecasting (WRF) and Community Multiscale Air Quality (CMAQ) models were used to simulate a 10 day high-ozone episode observed during the 2013 Uinta Basin Winter Ozone Study (UBWOS). The baseline model had a large negative bias when compared to ozone (O) and volatile organic compound (VOC) measurements across the basin. Contrary to other wintertime Uinta Basin studies, predicted nitrogen oxides (NO ) were typically low compared to measurements.

Evaluating a Space-Based Indicator of Surface Ozone-NO -VOC Sensitivity Over Midlatitude Source Regions and Application to Decadal Trends.

Determining effective strategies for mitigating surface ozone (O) pollution requires knowledge of the relative ambient concentrations of its precursors, NO , and VOCs. The space-based tropospheric column ratio of formaldehyde to NO (FNR) has been used as an indicator to identify NO -limited versus NO -saturated O formation regimes. Quantitative use of this indicator ratio is subject to three major uncertainties: (1) the split between NO -limited and NO -saturated conditions may shift in space and time, (2) the ratio of the vertically integrated column may not represent the near-surface environment, and (3) satellite products contain errors.

Coupling between Chemical and Meteorological Processes under Persistent Cold-Air Pool Conditions: Evolution of Wintertime PM Pollution Events and NO Observations in Utah's Salt Lake Valley.

The Salt Lake Valley experiences severe fine particulate matter pollution episodes in winter during persistent cold-air pools (PCAPs). We employ measurements throughout an entire winter from different elevations to examine the chemical and dynamical processes driving these episodes. Whereas primary pollutants such as NO and CO were enhanced twofold during PCAPs, O concentrations were approximately threefold lower.

Preliminary evaluation of the Community Multiscale Air Quality model for 2002 over the Southeastern United States.

The Visibility Improvement State and Tribal Association of the Southeast (VISTAS) is one of five Regional Planning Organizations that is charged with the management of haze, visibility, and other regional air quality issues in the United States. The VISTAS Phase I work effort modeled three episodes (January 2002, July 1999, and July 2001) to identify the optimal model configuration(s) to be used for the 2002 annual modeling in Phase II. Using model configurations recommended in the Phase I analysis, 2002 annual meteorological (Mesoscale Meterological Model [MM5]), emissions (Sparse Matrix Operator Kernal Emissions [SMOKE]), and air quality (Community Multiscale Air Quality [CMAQ]) simulations were performed on a 36-km grid covering the continental United States and a 12-km grid covering the Eastern United States.