Shortwave absorption by wildfire smoke dominated by dark brown carbon

Journal Article · 06 August 2023 · Nature Geoscience

DOI: https://doi.org/10.1038/s41561-023-01237-9 · OSTI ID:1993999

Chakrabarty, Rajan K. ; Shetty, Nishit J.; Thind, Arashdeep S. ; Beeler, Payton ; Sumlin, Benjamin J. ; Zhang, Chenchong ; Liu, Pai; Idrobo, Juan C. ; Adachi, Kouji ; Wagner, Nicholas L.; Schwarz, Joshua P. ; Ahern, Adam; Sedlacek, III, Arthur J. ; Lambe, Andrew ; Daube, Conner ; Lyu, Ming ; Liu, Chao ; Herndon, Scott; Onasch, Timothy B. ; Mishra, Rohan

Abstract Wildfires emit large amounts of black carbon and light-absorbing organic carbon, known as brown carbon, into the atmosphere. These particles perturb Earth’s radiation budget through absorption of incoming shortwave radiation. It is generally thought that brown carbon loses its absorptivity after emission in the atmosphere due to sunlight-driven photochemical bleaching. Consequently, the atmospheric warming effect exerted by brown carbon remains highly variable and poorly represented in climate models compared with that of the relatively nonreactive black carbon. Given that wildfires are predicted to increase globally in the coming decades, it is increasingly important to quantify these radiative impacts. Here we present measurements of ensemble-scale and particle-scale shortwave absorption in smoke plumes from wildfires in the western United States. We find that a type of dark brown carbon contributes three-quarters of the short visible light absorption and half of the long visible light absorption. This strongly absorbing organic aerosol species is water insoluble, resists daytime photobleaching and increases in absorptivity with night-time atmospheric processing. Our findings suggest that parameterizations of brown carbon in climate models need to be revised to improve the estimation of smoke aerosol radiative forcing and associated warming.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Archive
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Oceanic and Atmospheric Administration (NOAA); National Science Foundation (NSF); USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC05-00OR22725; SC0012704; SC0021011
• OSTI ID: 1993999
• Report Number(s): BNL--224797-2023-JAAM; PII: 1237
• Journal Information: Nature Geoscience, Journal Name: Nature Geoscience Journal Issue: 8 Vol. 16; ISSN 1752-0894
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English