Retrieval of ultraviolet aerosol absorption from radiation measurements in young wildfire plumes
- 1University of Colorado Boulder (Boulder, United States of America)
- 2University of California, Los Angeles (Los Angeles, United States of America)
Abstract
Aerosols play an important role for atmospheric radiative transfer in biomass burning (BB) plumes, where they control photochemistry, direct radiative forcing, and radiation-induced atmospheric dynamics. The optical properties of BB aerosol, however, remain poorly constrained with respect to their absorptive properties at ultraviolet and visible wavelengths. Aircraft-based observations show considerable variability due to heterogeneity in BB plumes, and different measurement methods do not agree with each other. To overcome this challenge, we have developed an algorithm based on the VLIDORT for photochemistry (VPC) radiative transfer model to retrieve the imaginary refractive index k ( λ ) from airborne actinic flux observations at wavelengths λ of 308–440 nm. Using three flights from NASA/NOAA’s Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) airborne experiment, we obtain values k (387 nm) between 0.02 and 0.03, and absorption Angstrom exponents α k between 3 and 5 for different transects. Volume absorption cross section (VAC) and single scattering albedo generally agree with aircraft-based observations, but show less variability, most likely because of the inherent spatial averaging of our observations. k ( λ ), VAC and single-scattering co-albedo decrease with physical plume age, with half-lives τ1/2 of 13±3, 16±4 and 17±4 h, respectively. Based on our observations, we present a parameterization of the absorptive properties of BB aerosol from western US wildfires as a function of wavelength and plume age, which will help to improve the representation of BB aerosol in models.
Versions
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BibTeX
@article{tirpitz2026retrieval,
title = {{Retrieval of ultraviolet aerosol absorption from radiation measurements in young wildfire plumes}},
author = {Jan-Lukas Tirpitz and Nathaniel Brockway and Santo Fedele Colosimo and Robert Spurr and Matt Christi and Samuel Hall and Kirk Ullmann and Vijay Natraj and Nicolas Theys and Johnathan Hair and Taylor Shingler and Rodney Weber and Ruchen Zhu and Jack Dibb and Richard Moore and Elizabeth Wiggins and Jochen Stutz},
journal = {Atmospheric Chemistry and Physics},
year = {2026},
month = nov,
doi = {10.5194/acp-26-15423-2026},
url = {https://doi.org/10.5194/acp-26-15423-2026},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Retrieval of ultraviolet aerosol absorption from radiation measurements in young wildfire plumes
AU - Jan-Lukas Tirpitz
AU - Nathaniel Brockway
AU - Santo Fedele Colosimo
AU - Robert Spurr
AU - Matt Christi
AU - Samuel Hall
AU - Kirk Ullmann
AU - Vijay Natraj
AU - Nicolas Theys
AU - Johnathan Hair
AU - Taylor Shingler
AU - Rodney Weber
AU - Ruchen Zhu
AU - Jack Dibb
AU - Richard Moore
AU - Elizabeth Wiggins
AU - Jochen Stutz
PY - 2026
DA - 2026/11/03
JO - Atmospheric Chemistry and Physics
DO - 10.5194/acp-26-15423-2026
UR - https://doi.org/10.5194/acp-26-15423-2026
AB - Aerosols play an important role for atmospheric radiative transfer in biomass burning (BB) plumes, where they control photochemistry, direct radiative forcing, and radiation-induced atmospheric dynamics. The optical properties of BB aerosol, however, remain poorly constrained with respect to their absorptive properties at ultraviolet and visible wavelengths. Aircraft-based observations show considerable variability due to heterogeneity in BB plumes, and different measurement methods do not agree with each other. To overcome this challenge, we have developed an algorithm based on the VLIDORT for photochemistry (VPC) radiative transfer model to retrieve the imaginary refractive index k ( λ ) from airborne actinic flux observations at wavelengths λ of 308–440 nm. Using three flights from NASA/NOAA’s Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) airborne experiment, we obtain values k (387 nm) between 0.02 and 0.03, and absorption Angstrom exponents α k between 3 and 5 for different transects. Volume absorption cross section (VAC) and single scattering albedo generally agree with aircraft-based observations, but show less variability, most likely because of the inherent spatial averaging of our observations. k ( λ ), VAC and single-scattering co-albedo decrease with physical plume age, with half-lives τ1/2 of 13±3, 16±4 and 17±4 h, respectively. Based on our observations, we present a parameterization of the absorptive properties of BB aerosol from western US wildfires as a function of wavelength and plume age, which will help to improve the representation of BB aerosol in models.
SN - 1680-7324
ER -