Measurements of size-resolved hygroscopicity in the California coastal zone D. A. Hegg1, D. S. Covert1, and H. H. Jonsson2 1Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA 2Meteorology Department, Naval Post Graduate School, Monterey, CA, USA
Abstract. Aircraft-based measurements of aerosol hygroscopicity, both in the form of
size-resolved, diameter growth factors and in the dependence of particle
light scattering on relative humidity, are presented for the marine boundary
layer of the southern California coastal zone. The chemical composition of
the aerosol is collated with the hygroscopicity data, both to examine the
mechanism for the increase in aerosol hygroscopicity with altitude and as
input for receptor type modeling. The data suggest an increase in aerosol
hygroscopicity with altitude, possibly associated with oxidation of organic
films. The receptor modeling suggests three distinct aerosol types/sources
for this venue: marine, biomass burning and pollution. Model output is used
in regression analyses to derive a prognostic mixing rule for the
hygroscopicity of aerosol with these three sources. The mixing rule
demonstrated substantial prognostic power for submicron hygroscopicity but
essentially none for supermicron.
Citation: Hegg, D. A., Covert, D. S., and Jonsson, H. H.: Measurements of size-resolved hygroscopicity in the California coastal zone, Atmos. Chem. Phys., 8, 7193-7203, doi:10.5194/acp-8-7193-2008, 2008.