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Regional and Seasonal Lightning NOx and Implications to Ground-Level Air Quality Over the Contiguous United States
Citation:
Kang, D., R. Mathur, L. Ran, G. Pouliot, David-C Wong, K. Foley, W. Appel, AND S. Roselle. Regional and Seasonal Lightning NOx and Implications to Ground-Level Air Quality Over the Contiguous United States. 2018 International Technical Meeting on Air Pollution Modelling and its Application, Ottawa, CANADA, May 14 - 18, 2018.
Impact/Purpose:
In order to develop efficient emission control strategies in State Implementation Plans that seek to attain National Ambient Air Quality Standards (NAAQS) for ozone and fine particulate matter (PM2.5) under the Clean Air Act, all sources of airborne precursors -- anthropogenic and natural -- should be considered. Nitric oxides (NOx) generated by lightning can contribute approximately 10% of the total NOx burden across the U.S. This presentation reports on a methodology to more accurately account for the generation of lightning NOx, which could improve simulations of chemical transport models like the Community Multiscale Air Quality (CMAQ) modeling system.
Description:
As one of the largest sources of natural NOX, it is estimated that lightning-induced NOX (LNOX) contributes 10-15% of the total global NOX emissions budget. Lightning activity exhibits strong spatial and temporal variations, and consequently so does the tropospheric distribution of NOX from lightning flashes. To assess the impact of LNOX on ground-level air quality, the Community Multiscale Air Quality (CMAQ) modeling system quantifies LNOX based on hourly gridded lightning strikes. The relative impact of LNOX on near-surface O3 depends not only on the extent and magnitude of lightning activity, but on NOX emissions from other sources, such as anthropogenic NOX and soil NO emissions. In this study, annual simulations for the year 2011 are performed using the WRF-CMAQ two-way coupled modeling system with and without LNOX. Total column lightning NOX and its relative contributions to total NOX emissions are quantified by region and time of year. The impact of LNOX on ground-level air quality is assessed by region and season based on evaluation against gas phase and deposition measurements, accounting for spatial differences in the relative importance of LNOX relative to other sources of NOX emissions
