Preprints
https://doi.org/10.5194/egusphere-2023-3114
https://doi.org/10.5194/egusphere-2023-3114
18 Jan 2024
 | 18 Jan 2024

Understanding Absorption by Black Versus Brown Carbon in Biomass Burning Plumes from the WE-CAN Campaign

Yingjie Shen, Rudra P. Pokhrel, Amy P. Sullivan, Ezra J. T. Levin, Lauren A. Garofalo, Delphine K. Farmer, Wade Permar, Lu Hu, Darin W. Toohey, Teresa Campos, Emily V. Fischer, and Shane M. Murphy

Abstract. Aerosol absorption of visible light has an important impact on global radiative forcing. Wildfires are one of the major sources of light-absorbing aerosol, but there remains significant uncertainty about the magnitude, wavelength dependence and bleaching of absorption from biomass burning aerosol. We collected and analyzed data from 21 Western United States wildfire smoke plumes during the 2018 WE-CAN airborne measurement campaign to determine the contribution of black carbon (BC), brown carbon (BrC), and lensing to the aerosol mass absorption cross-section (MAC). MACBC, MAC of organics (MACBrC+lensing), and the MAC of water-soluble BrC (MACws_BrC660) are calculated using Photoacoustic Absorption Spectrometer, Single Particle Soot Photometer and Particle-into-Liquid Sampler measurements. MACBC660 does not change significantly with physical age, organic aerosol (OA) concentration, oxygen to carbon ratio (O:C), gas-phase toluene:benzene ratio, modified combustion efficiency (MCE), altitude, or temperature, and has a relatively stable average value of 10.9 ± 2.1 m2 g-1. On average, 54 % of non-BC absorption (23 % total absorption) at 660 nm is from water-soluble BrC. MACws_BrC660 is 0.06 ± 0.04 m2 g-1 while MACBrC+lensing is 0.11 ± 0.06 m2 g-1 at 660 nm, increasing to 0.59 ± 0.19 m2 g-1 at 405 nm. MACBrC+lensing is constant with physical age and MCE, but increases slightly with increasing O:C or decreasing toluene:benzene, while total absorption (normalized to CO) slightly decreases with increasing O:C or decreasing toluene:benzene due to decreasing OA. No evidence of BrC bleaching is observed. Comparison to commonly used parameterizations, modeling studies, and the FIREX-AQ observations suggest model overestimation of absorption is likely due to incorrect BrC refractive indices. Quantification of significant brown carbon in the red wavelengths and the stability of MACBC, the observation of minimal bleaching, and the observation of changes in OA with O:C and toluene:benzene markers all serve as important constraints on aerosol absorption in regional and global climate models.

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Yingjie Shen, Rudra P. Pokhrel, Amy P. Sullivan, Ezra J. T. Levin, Lauren A. Garofalo, Delphine K. Farmer, Wade Permar, Lu Hu, Darin W. Toohey, Teresa Campos, Emily V. Fischer, and Shane M. Murphy

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-3114', Anonymous Referee #1, 03 Mar 2024
  • RC2: 'Comment on egusphere-2023-3114', Anonymous Referee #2, 03 Apr 2024
Yingjie Shen, Rudra P. Pokhrel, Amy P. Sullivan, Ezra J. T. Levin, Lauren A. Garofalo, Delphine K. Farmer, Wade Permar, Lu Hu, Darin W. Toohey, Teresa Campos, Emily V. Fischer, and Shane M. Murphy

Data sets

Aerosol Extinction, Scattering and Absorption (PAS CAPS) Data Shane M. Murphy https://doi.org/10.26023/K8P0-X4T3-TN06

Particle Into Liquid Sampler 2 (PILS2) two minute integrated cations, anions, levoglucosan, and organic acids data Amy P. Sullivan https://doi.org/10.26023/7TAN-TZMD-680Y

Single Particle Soot Photometer (SP2) Black Carbon Mass in Individual Particles Data Ezra J. T. Levin https://doi.org/10.26023/P8R2-RAB6-N814

CVI/UHSAS Data Darin W. Toohey https://doi.org/10.26023/BZ4F-EAC4-290W

PTR-ToF-MS Measurements of Selected NMVOCs Data Lu Hu and Wade Permar https://doi.org/10.26023/K9F4-2CNH-EQ0W

HR-ToF-AMS Fine-Mode Aerosol Composition Data Delphine K. Farmer and Sonia M. Kreidenweis https://doi.org/10.26023/MM2Y-ZGFQ-RB0B

Picarro G2401-m WS-CRDS CO2, CH4, CO and H2O in situ mixing ratio observations - ICARTT format Teresa Campos https://doi.org/10.26023/NNYM-Z18J-PX0Q

Aerodyne CS-108 miniQCL CO, N2O and H2O in situ mixing ratio observations - ICARTT format Teresa Campos https://doi.org/10.26023/Q888-WZRD-B70F

Yingjie Shen, Rudra P. Pokhrel, Amy P. Sullivan, Ezra J. T. Levin, Lauren A. Garofalo, Delphine K. Farmer, Wade Permar, Lu Hu, Darin W. Toohey, Teresa Campos, Emily V. Fischer, and Shane M. Murphy

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Short summary
The magnitude and evolution of Black Carbon (BC) and Brown Carbon (BrC) absorption with time remain unclear, causing uncertainty in climate models. Using data from the WE-CAN airborne measurement campaign, we show that absorption of BC from wildfire is relatively constant over time. BrC tends to be darker in more oxidated smoke plumes, challenging the idea that oxidation causes bleaching. We show that water-soluble BrC contributes 23 % of the total absorption at 660 nm.