Aerosols from biomass burning are recognized to perturb Earth’s
climate through the direct effect (both scattering and absorption of
incoming shortwave radiation), the semi-direct effect (evaporation of
cloud drops due to absorbing aerosols), and indirect effects (by
influencing cloud formation and precipitation. Biomass burning is an
important aerosol source, providing an estimated 40% of
anthropogenically influenced fine carbonaceous particles (Bond, et al.,
2004; Andrea and Rosenfeld, 2008). Primary organic aerosol (POA) from
open biomass burns and biofuel comprises the largest component of
primary organic aerosol mass emissions at northern temperate latitudes
(de Gouw and Jimenez, 2009). Data from the IMPROVE (Interagency
Monitoring of Protected Visual Environments; EPA 2012) network has been
used to show that in large sections of the U.S. aerosols from fires
(defined here to include agricultural burns and forest fires, both
prescribed and wild) are a major fraction of aerosol mass, and their
year-to-year variability dominates the overall variability of aerosol
loading and radiative forcing (Park, et al., 2007).
While many large field campaigns have studied biomass burning, the vast majority has focused on tropical regions (e.g., ABLE, BIBLE, PACE-5, SCAR-B, SAFARI92, SAFARI2000, TRACE-A, etc.) due to predictably of these events. In contrast, relatively fewer and smaller scale aircraft-based field campaigns focused on fire emissions have been carried out in the U.S., (e.g., Agaki, et al., 2012; Goode, et al., 2000; Burling, et al., 2011). The relatively infrequent occurrence of fires in the U.S. compared to the Amazon, Africa, and SE Asia (Wiedinmyer et al., 2011) has contributed to the comparative neglect of fire-related field campaigns in the U.S. This is particularly true when one excludes regional-scale campaigns in which biomass burning is sampled as a climatological component of the atmosphere, thousands of kilometers downwind of the source (e.g., Hecobian, et al., 2011). In intent of the Biomass Burn Observation Project (BBOP) is to conduct aircraft observations to study the near-field evolution of aerosol mixing state and morphology, black carbon mass absorption coefficients (MACs), chemical composition of non-refractory material associated with light absorbing carbon (LAC), production rate of secondary organic aerosol (SOA, microphysics processes relevant to determining aerosol size distributions and single scattering albedo (SSA), and CCN activity.
These research topics will be investigated through measurements near active fires (0-5 hours downwind), where limited observations indicate rapid changes in aerosol properties, and in biomass burning plumes aged >5 hours. Aerosol properties and their time evolution will be determined as a function of fire type, defined according to fuel and the mix of flaming and smoldering combustion at the source.
The DOE Gulfstream-1 aircraft (G-1) will be used for this field campaign from June 1 to October 30, 2013. During the summer months (June-August) the G-1 will be based at its home location in Pasco, Washington and then in the fall (October), operations will be moved to Memphis, Tennessee for a 4-week intensive operational period. A sampling strategy has been devised that will maximize opportunities to sample both fresh biomass burn emissions and aged plumes. The extended deployment of the G-1 in Pasco will target wildfires while the IOP in Memphis will focus on prescribed agricultural burns.
This field campaign will leverage the capabilities of several new instruments or instrument combinations that have not been previously used in aircraft. Morphological studies will be made by electron microscopy (offline) and Single-Particle Soot Photometer (SP2) analysis. Growth of particles with diameters < 60 nm will be determined by the high time resolution measurements provided by the Fast Integrated Mobility Spectrometer (FIMS). Quantitative measurements of the refractory and non-refractory components of particles containing BC will be provided by the Soot Particle Aerosol Mass Spectrometer (SP-AMS). Deployment of four instruments devoted to light absorption or extinction (Particle Soot Absorption Photometer (PSAP); Photothermal Interferometer (PTI); Photoacoustic Spectrometer (PAS); and Cavity Attenuated Phase Shift (CAPS)) will better quantify the inherently difficult aircraft measurement of light absorption and determination of mass absorption coefficients (MAC).
The primary measurement objective is to:
Quantify the time evolution of microphysical, morphological, chemical, hygroscopic, and optical properties of aerosols generated by biomass burning from near the time of formation onward.
The extended deployment at Pasco together with the IOP at Memphis will allow an examination of the dependence of evolution of biomass burn aerosol properties on fuel type. These properties will also be measured in plumes aged several days and compared with those of younger plumes.
The primary scientific objectives are to investigate:
These will be used to:
In the unlikely event that only a few fires can be sampled, a set of alternative objectives related to biogenic aerosols, new particle formation (NPF) and growth, and characteristics of black carbon-containing aerosols in various environments have been defined so that productive science can be done.
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