Although representing only a small mass fraction of the emissions from biomass burning, black carbon (BC) exerts a strong influence on climate. As a component of the atmospheric aerosol, BC absorbs visible light and warms the adjacent air, potentially altering the vertical temperature profile. If deposited to bright surfaces such as snow, BC may accelerate melting. Biomass burning is a large, but highly variable, global source of BC. Biomass burning emissions of BC are strongly correlated with increased flaming to smoldering ratios and likely correlated with increased combustion intensity, but these effects still need better quantification. A critical issue is that nearly all of the BC emitted by flaming combustion of biomass is found in particles that also contain much larger amounts of organic aerosol (OA) from smoldering combustion. The OA in the particles contributes to atmospheric cooling both directly, by reflecting solar radiation, and indirectly, by serving as cloud condensation nuclei that cause clouds to reflect more solar radiation. The increased solubility of particles containing water soluble OA makes them more likely to be removed from the atmosphere by rainfall. This reduces how long the particle can remain in the atmosphere and effect climate. Because of the co-emitted OA, biomass burning BC likely contributes less to global warming than an equal amount of BC emitted by fossil fuel combustion. In fact, aerosols from biomass burning are thought to have an overall cooling effect on climate, mitigating the warming associated with BC from that source. Further, the possibility that differences in the BC/OA ratio for wild and prescribed fires could lead to different climate impacts needs to be investigated. Any assessment of the climate impacts of biomass burning BC must consider the co-emitted OA. A major barrier to quantifying the climate impact of BC and OA emitted by wild and prescribed fires is that the traditional measurement methods for both BC and OA are filter-based and suffer from poor time resolution and numerous artifacts. We propose to measure the BC and OA emitted by the combustion of biomass with new, more accurate technology as part of an airborne platform that will sample smoke from one or more simulated wild fires at Fort Rucker, AL. The simulated wildfire(s) will be prescribed fires in unusually heavy fuel loads in unmanaged long leaf pine stands in November 2011. This proposal seeks support to augment the airborne laboratory with a soot photometer (SP2), an aerosol mass spectrometer (AMS), and a particle-into-liquid sampler (PILS) that will obtain accurate, high-time-resolution emission factor measurements for BC, OA, water soluble OA, and key smoke marker molecules. The measurements will complement the planned measurements of ozone and greenhouse gases on the aircraft. Based on known problems with earlier measurement methods, BC emissions inventories for prescribed and wild fires may have large errors that can be corrected using the new SP2 mass measurements. The SP2 also measures the BC emission heights, which affect the potential for long range transport; and the degree of coating of BC by other substances such as OA, which affects both aerosol optical properties and how readily the BC is removed in precipitation. Our measurements will represent the first high-resolution airborne BC/OA measurements for SE US wildfire(s). The project would also contribute to a database on plume injection altitudes for wild and prescribed fire. All the results will be incorporated in published, improved assessments of the climate impact of wild and prescribed fires.