Wildland Fires in CMAQ
Wild and prescribed (together called wildland) fires emit smoke that can strongly impact air quality both near the fire and far downwind. Wildland fires can also impact water bodies and soil when smoke particles settle out of the atmosphere or are removed through rainfall. Information about the type of trees in an area and the amount of the area that was burned is used to estimate wildland fire emissions. CMAQ then models how those emissions are transported downwind and react in the atmosphere.
The map above shows ozone produced from the Wallow Fire in Arizona in 2011 compared to the ozone produced from all emissions sources during the same time period.
Steps in the CMAQ Modeling Process:
- Wildland fire location and size are determined using satellite information and also reports from local, state, and federal agencies.
- Wildland fire emissions are based on vegetation amounts and vegetation-specific emission factors using the freely available Bluesky framework.
- Daily wildland fire emissions are input to CMAQ, which simulates transport, chemistry, and deposition.
- CMAQ outputs both ambient composition and deposition estimates for a multitude of pollutants including ozone (O3), particulate matter (PM), and air toxics (formaldehyde, mercury).
- CMAQ estimates of wildland fire impacts can be matched to places where people live to estimate community-based impacts on human health.
While emissions from fires have been treated in CMAQ for a number of years, observational studies have been infrequent and do not necessarily contain a large suite of measurements. Laboratory (FIREX) and field (FIREX-AQ, FASMEE) studies include unique instrumentation to characterize a large suite of compounds. Better characterization of emissions and ambient transformations can lead to more accurate and robust predictions of the impact of fires on air quality. Further refinements and improvements to the identification of fire types and the estimation of fire emissions in the modeling system is an ongoing process that continues to evolve.
Watch a time-lapse of CMAQ predicted PM2.5 concentrations from a wildland fire in California
References
Baker, K.R., Woody, M.C., Tonnesen, G.S., Hutzell, W., Pye, H.O.T., Beaver, M.R., Pouliot, G., & Pierce, T. (2016). Contribution of regional-scale fire events to ozone and PM2.5 air quality estimated by photochemical modeling approaches. Atmos. Environ., 140, 539-554.
Baker, K., Woody, M., Valin, L., Szykman, J., Yates, E., Iraci, L., Choi, H., Soja, A., Koplitz, S., Zhou, L. (2018). Photochemical model evaluation of 2013 California wild fire air quality impacts using surface, aircraft, and satellite data. Science of The Total Environment, 637, 1137-1149.
Zhou, L., Baker, K.R., Napelenok, S.L., Pouliot, G., Elleman, R., O'Neill, S.M., Urbanski, S.P., Wong, D.C. (2018). Modeling crop residue burning experiments to evaluate smoke emissions and plume transport. Science of The Total Environment, 627, 523-533.
Wilkins, J.L., Pouliot, G., Foley, K., Appel, W., Pierce, T. (2018). The impact of US wildland fires on ozone and particulate matter: a comparison of measurements and CMAQ model predictions from 2008 to 2012. International Journal of Wildland Fire, 27, 684-698.