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- Title
Spatially Resolved Photochemistry Impacts Emissions Estimates in Fresh Wildfire Plumes.
- Authors
Palm, Brett B.; Peng, Qiaoyun; Hall, Samuel R.; Ullmann, Kirk; Campos, Teresa L.; Weinheimer, Andrew; Montzka, Deedee; Tyndall, Geoffrey; Permar, Wade; Hu, Lu; Flocke, Frank; Fischer, Emily V.; Thornton, Joel A.
- Abstract
Wildfire emissions affect downwind air quality and human health. Predictions of these impacts using models are limited by uncertainties in emissions and chemical evolution of smoke plumes. Using high‐time‐resolution aircraft measurements, we illustrate spatial variations that can exist within a plume due to differences in the photochemical environment. Horizontal and vertical crosswind gradients of dilution‐corrected mixing ratios were observed in midday plumes for reactive compounds and their oxidation products, such as nitrous acid, catechol, and ozone, likely due to faster photochemistry in optically thinner plume edges relative to darker plume cores. Gradients in plumes emitted close to sunset are characterized by titration of O3 in the plume and reduced or no gradient formation. We show how crosswind gradients can lead to underestimated emission ratios for reactive compounds and overestimated emission ratios for oxidation products. These observations will lead to improved predictions of wildfire emissions, evolution, and impacts across daytime and nighttime. Plain Language Summary: Wildfire emissions have large impacts on air quality and health in downwind communities. Previous research has shown that chemical reactions in fire plumes can be remarkably fast, which modifies the impact the smoke has downwind. In this work, we show how this chemistry happens faster on the edges versus the core of plumes emitted during midday. For plumes emitted near or after sunset, oxidation chemistry generally slows and remains nearly uniform across the plume. These variations in plume chemistry will impact how plumes are modeled, and how well we can predict downwind air quality impacts. Key Points: Spatial gradients are observed in dilution‐corrected mixing ratios of nitrous acid, ozone, and reactive organics in fresh wildfire plumesGradients evolve with time of day, as intensity of chemical aging varies relative to plume transport and mixingGradients should be considered when comparing plume models with measurements and estimating fire emissions from in situ observations
- Subjects
SMOKE plumes; PHOTOCHEMISTRY; WILDFIRES; AIR quality; NITROUS acid; WILDFIRE prevention
- Publication
Geophysical Research Letters, 2021, Vol 48, Issue 23, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2021GL095443