Atmos. Chem. Phys. Discuss., 12, 2483-2516, 2012
© Author(s) 2012. This work is distributed
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Laboratory measurements and model sensitivity studies of dust deposition ice nucleation
G. Kulkarni, J. Fan, J. M. Comstock, X. Liu, and M. Ovchinnikov
Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA

Abstract. We investigated the ice nucleating properties of mineral dust particles to understand the sensitivity of modeled cloud properties to different representations of contact angle in the Classical Nucleation Theory (CNT): onset single angle and probability density function (PDF) distribution approaches. These contact angle representations are based on two sets of laboratory deposition ice nucleation measurements: Arizona Test Dust (ATD) particles of 100, 300, and 500 nm sizes were tested at three different temperatures (−25, −30 and −35 °C), and 400 nm ATD and Kaolinite dust species were tested at two different temperatures (−30 and −35 °C). These measurements were used to derive the onset relative humidity with respect to ice (RHice) required to activate 1% of dust particles as ice nuclei, from which the onset single contact angles were then calculated based on the CNT. For the PDF representation, parameters of the log-normal contact angle distribution (mean and standard deviation) were determined by fitting the CNT-predicted activated fraction to the measurements at different RHice. Results show that onset single contact angles are not much different between experiments, while the PDF parameters are sensitive to those environmental conditions (i.e., temperature and dust size). The cloud resolving model simulations show that cloud properties (i.e. ice number concentration, ice water content, and cloud initiation times) are sensitive to onset single contact angles and PDF distribution parameters, particularly to the mean value. The comparison of our experimental results with other studies shows that under similar measurement conditions the onset single contact angles are consistent within ±2.0°, while our derived PDF parameters have discrepancies.

Citation: Kulkarni, G., Fan, J., Comstock, J. M., Liu, X., and Ovchinnikov, M.: Laboratory measurements and model sensitivity studies of dust deposition ice nucleation, Atmos. Chem. Phys. Discuss., 12, 2483-2516, doi:10.5194/acpd-12-2483-2012, 2012.
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