Heat flux assumptions contribute to overestimation of wildfire smoke injection into the free troposphere

Injections of wildfire smoke plumes into the free troposphere impact air quality, yet model forecasts of injections are poor. Here, we use aircraft observations obtained during the 2019 western US wildfires (FIREX-AQ) to evaluate a commonly used smoke plume rise parameterization in two atmospheric c...

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Bibliographic Details
Published in:Communications earth & environment 2022-12, Vol.3 (1), p.1-11, Article 236
Main Authors: Thapa, Laura H., Ye, Xinxin, Hair, Johnathan W., Fenn, Marta A., Shingler, Taylor, Kondragunta, Shobha, Ichoku, Charles, Dominguez, RoseAnne, Ellison, Luke, Soja, Amber J., Gargulinski, Emily, Ahmadov, Ravan, James, Eric, Grell, Georg A., Freitas, Saulo R., Pereira, Gabriel, Saide, Pablo E.
Format: Article
Language:English
Subjects:
Air quality
Aircraft
Atmospheric chemistry
Atmospheric models
Boundary layers
Fluctuations
Heat
Heat flux
Heat transfer
Parameterization
Planetary boundary layer
Plumes
Smoke
Temperature
Troposphere
Wildfires
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Summary:Injections of wildfire smoke plumes into the free troposphere impact air quality, yet model forecasts of injections are poor. Here, we use aircraft observations obtained during the 2019 western US wildfires (FIREX-AQ) to evaluate a commonly used smoke plume rise parameterization in two atmospheric chemistry-transport models (WRF-Chem and HRRR-Smoke). Observations show that smoke injections into the free troposphere occur in 35% of plumes, whereas the models forecast 59–95% indicating false injections in the simulations. False injections were associated with both models overestimating fire heat flux and terrain height, and with WRF-Chem underestimating planetary boundary layer height. We estimate that the radiant fraction of heat flux is 0.5 to 25 times larger in models than in observations, depending on fuel type. Model performance was substantially improved by using observed heat flux and boundary layer heights, confirming that models need accurate heat fluxes and boundary layer heights to correctly forecast plume injections.
ISSN:2662-4435
2662-4435
DOI:10.1038/s43247-022-00563-x