Understanding the Evolution of Biomass Burning Particles in the Atmosphere: Analysis of BBOP Data, Laboratory Experiments and Model Integration

Principal Investigator(s):
Leah Williams, Aerodyne Research Inc.

Co-Investigator(s):
Dr. Timothy Onasch, Aerodyne Research, Inc.
Dr. Douglas Worsnop, Aerodyne Research, Inc.
Dr. Robert Yokelson, University of Montana
Dr. Peter Buseck, Arizona State University

Biomass burning aerosols (BBA) are a major contributor to the total global aerosol budget of black carbon (BC) and organic carbon (OC), including light absorbing brown carbon (BrC). BBA are generated in the uncontrolled and often incomplete combustion of biomass and biofuels. The physiochemical properties of the emitted BBA particles vary widely and can change significantly through atmospheric processing. These variable properties govern BBA absorption of visible light in the atmosphere, directly affecting the earth’s radiation balance, and determine how BBA particles indirectly affect climate through changes to cloud particle formation and properties, affecting cloud albedo, coverage, and lifetime. The uncertainties in our understanding of the physical, chemical, and optical properties of BBA particles mean that their impacts are poorly represented in climate models.

The DOE Atmospheric Radiation Measurement (ARM) Biomass Burning Observation Project (BBOP) field campaign during the summer and fall of 2013 yielded a unique, extremely detailed set of trace gas and aerosol measurements in biomass burning plumes from wildfires in the northwest U.S. and from prescribed agricultural burns in the southeast U.S., including valuable information on downwind transformations close to the sources. The first part of this project will analyze data from BBOP and relate the airborne measurements to simultaneous measurements at the Mount Bachelor Observatory. The second part of the project will entail laboratory experiments to generate and characterize tar balls from biomass burning fuels. Although often observed in biomass burning plumes, the physical, chemical, and optical properties of tar balls are poorly understood and their contribution to the climate impact of biomass burning plumes is not known. The third part of the project aims to incorporate new understanding about the properties and transformations of BBA into an aerosol box model and then into regional climate models. The overall research project will enhance the understanding of the lifecycle of BBA, improving both their representation in regional and global climate models and the techniques for future BBA measurements under ambient conditions.