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GEOPHYSICAL RESEARCH LETTERS,
VOL. 33,
L02810,
doi:10.1029/2005GL024052,
2006
Analytical expression for the relative dispersion of the cloud droplet size distribution
Yangang Liu
Brookhaven National Laboratory, Upton, New York, USA
Peter H. Daum
Brookhaven National Laboratory, Upton, New York, USA
Seong Soo Yum
Department of Atmospheric Sciences, Yonsei University, Seoul, South Korea
Abstract
An analytical expression that relates the relative dispersion (ratio of standard deviation to mean radius) of the cloud droplet
size distribution to CCN spectra and updraft velocity is derived from adiabatic growth theory of cloud droplets. Coupled with
the Twomey expression for droplet concentration, the analytical expression is used to examine the relationship of relative
dispersion to droplet concentration under different combinations of CCN spectra and updraft velocities. These analytical results
compare favorably with the corresponding simulations of an adiabatic parcel model. The analytical expression theoretically
demonstrates that an increase in aerosol loading (CCN concentration) leads to concurrent increases in the droplet concentration
and relative dispersion whereas a larger updraft velocity leads to a higher droplet concentration but a smaller relative dispersion.
Received 12
July
2005;
accepted 14
December
2005;
published 26
January
2006.
Index Terms: 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 1640 Global Change: Remote sensing (1855); 1704 History of Geophysics: Atmospheric sciences.
Read Full Article (file size: 92849 bytes) Cited by
Citation: Liu, Y., P. H. Daum, and S. S. Yum
(2006),
Analytical expression for the relative dispersion of the cloud droplet size distribution,
Geophys. Res. Lett.,
33,
L02810,
doi:10.1029/2005GL024052.
Copyright 2006 by the American Geophysical Union.
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