Optical particle counter measurement of marine aerosol hygroscopic growth J. R. Snider1 and M. D. Petters2 1Department of Atmospheric Science Dept. 3038, University of Wyoming, 1000 East University Avenue, Laramie, WY 82071, USA 2Department of Atmospheric Science 1371, Colorado State University, Campus Delivery Fort Collins, CO 80523-1371, USA
Abstract. A technique is developed for the determination of the hygroscopic growth
factor of dry particles with diameter between 0.3 and 0.6 μm and is
applied to measurements made during the second Dynamics and Chemistry of Marine
Stratocumulus experiment (DYCOMS-II). Two optical particle counters are utilized,
one measures the aerosol size spectrum at ambient relative humidity and the
other simultaneously dries the aerosol prior to light scattering detection.
Growth factors are based on measurements made in the region of the Mie
scattering curve where scattered light intensity increases monotonically
with dry and wet particle diameter, i.e. D<0.9 μm. Factors
influencing the accuracy of the measurement are evaluated, including
particle drying, refractive index and shape. Growth factors at 90±3%
ambient relative humidity in marine airmasses 400 km west of San Diego,
California range between 1.5 and 1.8. This suggests that a significant
fraction of the particle mass, between 40 and 70%, is either
non-hygroscopic or weakly hygroscopic.
Citation: Snider, J. R. and Petters, M. D.: Optical particle counter measurement of marine aerosol hygroscopic growth, Atmos. Chem. Phys., 8, 1949-1962, doi:10.5194/acp-8-1949-2008, 2008.