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Characterizing the Influence of Hemispheric Transport on Regional Air Pollution
Citation:
Mathur, R., J. Xing, D. Kang, S. Napelenok, C. Hogrefe, G. Sarwar, AND Jon Pleim. Characterizing the Influence of Hemispheric Transport on Regional Air Pollution. 10th International Conf. on Air Quality-Science & Application, Milan, ITALY, March 14 - 18, 2016.
Impact/Purpose:
The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates data, decision-support tools, and models to be applied to media-specific or receptor-specific problem areas. CED uses modeling-based approaches to characterize exposures, evaluate fate and transport, and support environmental diagnostics/forensics with input from multiple data sources. It also develops media- and receptor-specific models, process models, and decision support tools for use both within and outside of EPA.
Description:
Expansion of the coupled WRF-CMAQ modeling system to hemispheric scales is pursued to enable the development of a robust modeling framework in which the interactions between atmospheric processes occurring at various spatial and temporal scales can be examined in a consistent manner. The WRF-CMAQ modeling system was applied over a domain encompassing the northern hemisphere. The horizontal domain, set on a polar stereographic projection, was discretized using grid cells with a 108 km resolution, while the vertical extent ranging from the surface to 50 mb was discretized with 44 layers of variable thickness with a 20 m deep lowest layer. Emissions of NOx, SO2, CO, volatile organic compounds, and particulate matter from anthropogenic, biomass burning, and biogenic sources were derived from existing global inventories. Model simulations for the 1990-2010 period and numerous associated sensitivity simulations (examining impacts of vertical layer structure, stratospheric O3 influences, representation of NOx recycling through organic nitrates, halogen chemistry in marine environments) have been conducted to establish the capability to exercise CMAQ over the Northern hemisphere. CMAQ configured with the direct decoupled method is used to estimate source region contributions to O3 levels in the receptor region. These are then combined with the multi-decadal simulations to delineate the trends in the relative contributions of different source regions across the northern hemisphere to background O3 levels in the U.S.
