Abstract
A modeling study of the effect of drizzle on cloud optical depth and susceptibility
Cooperative Institute for Research in the Atmosphere and NOAA Environmental Technology Laboratory Boulder, Colorado
Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia
Department of Atmospheric Science, Colorado State University, Fort Collins
Department of Atmospheric Science, Colorado State University, Fort Collins
This paper examines the impact of drop spectral broadening, generated by the collection process, on the optical depth, cloud albedo, and susceptibility of marine stratocumulus clouds. The results are arrived at using (1) the output from a simple box model calculation of collection and (2) the output from an eddy-resolving model of stratocumulus clouds that explicitly represents the size distribution of the drops. It is shown that commonly used relationships for cloud optical properties developed for narrow spectra do not generally apply to spectra undergoing spectral broadening. The optical depth dependence on the drop number concentration to the one-third power is shown to be an overestimate of the optical depth when spectra broaden through collection. In addition, the cloud susceptibility dependence on drop number is shown to be larger for spectra experiencing broadening than for narrow spectra.
Received 20 November 1996; accepted 26 March 1997; .
Citation: (1997), A modeling study of the effect of drizzle on cloud optical depth and susceptibility, J. Geophys. Res., 102(D12), 13,527–13,534.
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