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Published August 2010 | Published
Journal Article Open

In Situ Chemical Characterization of Aged Biomass-Burning Aerosols Impacting Cold Wave Clouds


During the Ice in Clouds Experiment–Layer Clouds (ICE-L), aged biomass-burning particles were identified within two orographic wave cloud regions over Wyoming using single-particle mass spectrometry and electron microscopy. Using a suite of instrumentation, particle chemistry was characterized in tandem with cloud microphysics. The aged biomass-burning particles comprised ~30%–40% by number of the 0.1–1.0-μm clear-air particles and were composed of potassium, organic carbon, elemental carbon, and sulfate. Aerosol mass spectrometry measurements suggested these cloud-processed particles were predominantly sulfate by mass. The first cloud region sampled was characterized by primarily homogeneously nucleated ice particles formed at temperatures near −40°C. The second cloud period was characterized by high cloud droplet concentrations (~150–300 cm^(−3)) and lower heterogeneously nucleated ice concentrations (7–18 L^(−1)) at cloud temperatures of −24° to −25°C. As expected for the observed particle chemistry and dynamics of the observed wave clouds, few significant differences were observed between the clear-air particles and cloud residues. However, suggestive of a possible heterogeneous nucleation mechanism within the first cloud region, ice residues showed enrichments in the number fractions of soot and mass fractions of black carbon, measured by a single-particle mass spectrometer and a single-particle soot photometer, respectively. In addition, enrichment of biomass-burning particles internally mixed with oxalic acid in both the homogeneously nucleated ice and cloud droplets compared to clear air suggests either preferential activation as cloud condensation nuclei or aqueous phase cloud processing.

Additional Information

© 2010 American Meteorological Society. Received: September 23, 2009; Accepted: January 21, 2010. NSF and NCAR are acknowledged for financial support of the ICE-L field campaign, as well as the work of A. J. Heymsfield. K. A. Pratt and K. A. Prather acknowledge NSF for support of ICE-L (ATM- 0650659), A-ATOFMS development (ATM-0321362), and a graduate research fellowship for K. A. Pratt. S. M. Murphy and J. H. Seinfeld acknowledge NSF for support of ICE-L (ATM-0340832) and NASA for an Earth and Space Sciences Fellowship for S. M. Murphy. C. H. Twohy, P. J. DeMott, J. G. Hudson, R. Subramanian, and Z. Wang acknowledge NSF for ICE-L support (ATM-0612605, ATM-0611936, ATM-0615414, ATM- 0631919, and ATM-0645644, respectively). CVI sampling was performed by Rich Cageo. STEM-EDX analysis was completed by Traci Lersch (RJ Lee Group, Inc.). Jeffrey R. French and Samuel Haimov (University of Wyoming) assisted with lidar and radar data. Teresa Campos (NCAR) provided carbon monoxide and TDL hygrometer data. Cloud probe data were provided by NCAR/EOL under the sponsorship of NSF (http://data.eol.ucar.edu).

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