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Laboratory and field studies have identified biomass burning as a potentially important contributor to the global atmospheric heterogeneous ice nuclei (IN) reservoir. However, IN production from biomass burning is poorly characterized and dependent upon changes in aerosol properties associated with differences in fuel type, combustion efficiency, and/or plume aging. Measurements from four prescribed burns, two wildfires and laboratory studies support biomass burning as a potential source of IN to the atmosphere, and have provided insight regarding the characteristics of IN emitted from biomass burning sources. more...

We measured size-resolved CCN concentrations over an annual cycle and during a summer intensive study at a remote, forested location in Colorado. From these data we derived aerosol hygroscopicity and size-resolved two-component composition. During the summer intensive, aerosol composition was also measured with an aerosol mass spectrometer, and we use these data to confirm hygroscopicity-derived composition. Throughout the study and at all measured sizes, aerosol composition was predominately organic with resulting low hygroscopicity, κave = 0.16 ± 0.08. New particle formation appeared to be an important source of aerosol number and the newly nucleated particles were inferred to be predominately organic. more...