BBOP

Biomass Burning Observation Project (BBOP)

1 July 2013 - 24 October 2013

Lead Scientist: Larry Kleinman

Observatory: AAF, OSC

This field campaign addressed multiple uncertainties in aerosol intensive properties, which are poorly represented in climate models, by means of aircraft measurements in biomass burning plumes. Key topics investigated were:

1. Aerosol mixing state and morphology
2. Mass absorption coefficients (MACs)
3. Chemical composition of non-refractory material associated with light-absorbing carbon (LAC)
4. Production rate of secondary organic aerosol (SOA)
5. Microphysical processes relevant to determining aerosol size distributions and single scattering albedo (SSA)
6. CCN activity.

These topics were 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 were determined as a function of fire type, defined according to fuel and the mix of flaming and smoldering combustion at the source. The DOE G-1 aircraft was requested from June 1 to October 30, 2013, to be based at its home location in Pasco, Washington, except for a 4-week intensive operational period (IOP) in Little Rock, Arkansas. A sampling strategy was devised that maximized opportunities to sample both fresh biomass burn emissions and aged plumes. This strategy consisted of an extended deployment of the G-1 in Pasco from July 1 – August 31, 2013, during which time targets of opportunity were exploited, and an IOP in Little Rock in September-October 2013, where prescribed agricultural burns were sampled. This field campaign leveraged the capabilities of several new instruments or instrument combinations that were not previously used in aircraft. Morphological studies were made by electron microscopy (offline) and Single-Particle Soot Photometer (SP2) analysis. Growth of particles with diameters < 60 nm were 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 were 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)) better quantified the inherently difficult aircraft measurement of light absorption and determination of mass absorption coefficients (MAC). The primary measurement objective was 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 Little Rock allows an examination of the dependence of evolution of biomass burn aerosol properties on fuel type. These properties were also be measured in plumes aged several days and compared with those of younger plumes. The primary scientific objectives were to investigate:

• SOA Formation Rates
• Structure and/or Configuration of Biomass Burn Aerosol Particles
• Aerosol Light Absorption
• Composition of Brown Carbon (BrC)
• Time Evolution of the Composition of Refractory Black Carbon (rBC)
• Determination of Mass Absorption Coefficients (MAC)
• Determination of the Time-Series for Coagulation and Condensation
• CCN Evolution, and Relation to Condensed Organics
• Radiative Transfer of Biomass Burns.

These will be used to:

• Constrain processes and parameterizations in a detailed Lagrangian model to reproduce the time-dependent microphysics and chemistry of aerosol evolution
• Incorporate time evolution information into a single-column radiative model as a first step in translating observations into a forcing per unit mass carbon burned.