Grantee Research Project Results
2017 Progress Report: Interplay Between Black and Brown Carbon from Biomass Burning and Climate
EPA Grant Number: R835883Title: Interplay Between Black and Brown Carbon from Biomass Burning and Climate
Investigators: Murphy, Shane Michael
Institution: University of Wyoming
EPA Project Officer: Chung, Serena
Project Period: January 1, 2016 through December 31, 2018 (Extended to September 30, 2020)
Project Period Covered by this Report: January 1, 2017 through December 31,2017
Project Amount: $349,847
RFA: Particulate Matter and Related Pollutants in a Changing World (2014) RFA Text | Recipients Lists
Research Category: Air , Climate Change , Early Career Awards
Objective:
The objectives of this project are to determine the wavelength-resolved single scattering albedo (SSA), absorption and extinction, along with the chemical and physical properties of aerosol emissions from biomass burning (wildfires) in the Western United States. These data enable us to determine the contribution of black versus brown carbon to observed aerosol absorption and quantify the enhancement of black carbon absorption caused by organic coatings. We utilize these new in-situ observations to update the refractive indices of organic and black carbon aerosol from biomass burning in the NCAR Community Atmosphere Model (CAM5) and assess the regional and global climate impacts of improved optical properties under a range of future biomass burning scenarios. In particular, we investigate the current and future radiative forcing and climatic effect from brown carbon absorption utilizing CAM5.
Progress Summary:
The major accomplishments during this reporting period are as follow:
- The mass absorption coefficient, which quantifies how much light brown carbon absorbs, of the ambient brown carbon is found to be 0.4–0.8 m2/g.
- Ambient measurements of brown carbon show that a large fraction of absorption is due to low-volatility organics, which account for 5–20 percent of the total aerosol volume.
- SSA parameterization via the black carbon:total carbon ratio shows consistency between laboratory and ambient studies.
- Implementation of the brown carbon parameterization in CAM5 yields similar forcing to estimates to those from chemical transport models.
- Implementation of brown carbon in CAM5 improves the absorption angstrom exponent estimates over biomass-burning regions.
- CAM5 SSA estimates are low over biomass-burning regions compared to field measurements.
It is critical to understand and improve the optical properties of biomass burning emissions in global models to have confidence in this forcing in future climates where biomass burning emissions will be a significant forcing agent. All of the results given above contribute significantly to our understanding of how to more accurately include biomass burning emissions into the radiative balance.
Future Activities:
During the next reporting period our major activity will again deploy the University of Wyoming mobile lab equipped with the 4-wavelength photoacoustic absorption spectrometer, 2-wavelength cavity attenuated phase shift–SSA, scanning mobility particle sizers and aerosol mass spectrometer instruments to multiple wildfires in the Western United States to increase the statistical significance of our findings to date. We also plan to publish three to four peer-reviewed papers covering novel calibration procedures, a summary of the first set of field deployments, a description of the results of adding brown carbon to the CAM5 global climate model, and a paper exploring differences in SSA between the CAM5 climate model and ambient observations. The paper describing implementation of brown carbon into the CAM5 global climate model has already been submitted and is currently being revised to include a parameterization for bleaching of brown carbon absorption with photochemical aging.
Journal Articles:
No journal articles submitted with this report: View all 6 publications for this projectSupplemental Keywords:
Air, tropospheric, atmosphere, climate modelsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.