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Uniform particle-droplet partitioning of 18 organic and elemental components measured in and below DYCOMS-II stratocumulus clouds

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Title Uniform particle-droplet partitioning of 18 organic and elemental components measured in and below DYCOMS-II stratocumulus clouds
Names Hawkins, L. N. (creator)
Russell, L. M. (creator)
Twohy, Cynthia (creator)
Anderson, J. R. (creator)
Date Issued 2008 (iso8601)
Note copyrighted by American Geophysical Union
Abstract Microphysical and chemical aerosol measurements collected during DYCOMS-II
research flights in marine stratocumulus clouds near San Diego in 2001 were used to
evaluate the partitioning of 18 organic and elemental components between droplet
residuals and unactivated particles. Bulk submicron particle (between 0.2 and 1.3 μm dry
diameter) and droplet residual (above 9 μm ambient diameter) filter samples analyzed by
Fourier Transform Infrared (FTIR) spectroscopy and X-ray Fluorescence (XRF) were
dominated by sea salt, ammonium, sulfate, and organic compounds. For the four nighttime
and two daytime flights studied, the mass concentration of unactivated particles and
droplet residuals were correlated (R² > 0.8) with consistent linear relationships for mass
scavenging of all 18 components on each flight, meaning that the measured particle
population partitions between droplet residuals and unactivated particles as if the particles
contain internal mixtures of the measured components. Scanning electron microscopy
(SEM) for flights 3, 5, and 7 support some degree of internal mixing since more than 90%
of measured submicron particles larger than 0.26 μm included sea salt-derived
components. The observed range of 0.26 to 0.40 of mass scavenging coefficients for the
four nighttime flights results from the small variations in temperature profile, updraft
velocity, and mixed layer depth among the flights. The uniformity of scavenging
coefficients for multiple chemical components is consistent with the aged or processed
internal mixtures of sea salt, sulfate, and organic compounds expected at long distances
downwind from major particle sources.
Genre Article
Identifier Hawkins, L, Russell, L. M., Twohy, C. H. and Anderson, J. R., 2008, Uniform particle-droplet partitioning of 18 organic and elemental components measured in and below DYCOMS-II stratocumulus clouds: J. Geophys. Res., v. 113, D14201.

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