3D Air Quality and the Clean Air Interstate Rule: Lagrangian Sampling of CMAQ Model Results to Aid Regional Accountability Metrics

The Clean Air Interstate Rule (CAIR) is expected to reduce transport of air pollutants (e.g. fine sulfate particles) in nonattainment areas in the Eastern United States. CAIR highlights the need for an integrated air quality observational and modeling system to understand sulfate as it moves in multiple dimensions, both spatially and temporally. Here, we demonstrate how results from an air quality model can be combined with a 3d monitoring network to provide decision makers with a tool to help quantify the impact of CAIR reductions in SO2 emissions on regional transport contributions to sulfate concentrations at surface monitors in the Baltimore, MD area, and help improve decision making for strategic implementation plans (SIPs). We sample results from the Community Multiscale Air Quality (CMAQ) model using ensemble back trajectories computed with the NASA Langley Research Center trajectory model to provide Lagrangian time series and vertical profile information, that can be compared with NASA satellite (MODIS), EPA surface, and lidar measurements. Results are used to assess the regional transport contribution to surface SO4 measurements in the Baltimore MSA, and to characterize the dominant source regions for low, medium, and high SO4 episodes

Chemical data assimilation estimates of continental U.S. ozone and nitrogen budgets during the Intercontinental Chemical Transport Experiment-North America

Global ozone analyses, based on assimilation of stratospheric profile and ozone column measurements, and NOy predictions from the Real-time Air Quality Modeling System (RAQMS) are used to estimate the ozone and NOy budget over the continental United States during the July-August 2004 Intercontinental Chemical Transport Experiment-North America (INTEX-A). Comparison with aircraft, satellite, surface, and ozonesonde measurements collected during INTEX-A show that RAQMS captures the main features of the global and continental U.S. distribution of tropospheric ozone, carbon monoxide, and NOy with reasonable fidelity. Assimilation of stratospheric profile and column ozone measurements is shown to have a positive impact on the RAQMS upper tropospheric/lower stratosphere ozone analyses, particularly during the period when SAGE III limb scattering measurements were available. Eulerian ozone and NOy budgets during INTEX-A show that the majority of the continental U.S. export occurs in the upper troposphere/lower stratosphere poleward of the tropopause break, a consequence of convergence of tropospheric and stratospheric air in this region. Continental U.S. photochemically produced ozone was found to be a minor component of the total ozone export, which was dominated by stratospheric ozone during INTEX-A. The unusually low photochemical ozone export is attributed to anomalously cold surface temperatures during the latter half of the INTEX-A mission, which resulted in net ozone loss during the first 2 weeks of August. Eulerian NOy budgets are shown to be very consistent with previously published estimates. The NOy export efficiency was estimated to be 24%, with NOx + PAN accounting for 54% of the total NOy export during INTEX-A. Copyright 2007 by the American Geophysical Union

Challenges and Opportunities for Remote Sensing of Air Quality: Insights from DISCOVER-AQ

No abstract availabl

Impacts of Background Ozone Production on Houston and Dallas, Texas, Air Quality During the Second Texas Air Quality Study Field Mission

A major objective of the 2006 Second Texas Air Quality Study (TexAQS II) focused on understanding the effects of regional processes on Houston and Dallas ozone nonattainment areas. Here we quantify the contributions of background (continental scale) ozone production on Houston and Dallas air quality during TexAQS II using ensemble Lagrangian trajectories to identify remote source regions that impact Houston and Dallas background ozone distributions. Global-scale chemical analyses, constrained with composition measurements from instruments on the NASA Aura satellite, are used to provide estimates of background composition along ensemble back trajectories. Lagrangian averaged O-3 net photochemical production (production minus loss, P-L) rates along the back trajectories are used as a metric to classify back trajectories. Results show that the majority (6 out of 9 or 66%) of the periods of high ozone in Houston were associated with periods of enhanced background ozone production. Slightly less than 50% (7 out of 15) of the days with high ozone in the Dallas Metropolitan Statistical Area (MSA) show enhanced background ozone production. Source apportionment studies show that 5-day Lagrangian averaged O-3 P-L in excess of 15 ppbv/d can occur during continental-scale transport to Houston owing to NOy enhancements from emissions within the Southern Great Lakes as well as recirculation of the Houston emissions. Dallas background O-3 P-L is associated with NOy enhancements from emissions within Chicago and Houston