LINEAR EDDY MODELING OF DROPLET SPECTRAL EVOLUTION DURING ENTRAINMENTAND MIXING IN CUMULUS CLOUDS

The explicit mixing parcel model (EMPM) of Krueger et al. [Krueger, S. K., Su, C.-W., McMurtry, P,A., 1997. Modeling entrainment and fine-sca le mixing in cumulus clouds. J. Atmos. Sci. 54, 2697-2712.] is extende d to explicitly account for individual droplet growth. The model provi des a 1D representation of physical properties within a cloud parcel a nd incorporates the rising of the cloud parcel, entrainment of environ mental air into the parcel, finite-rate turbulent mixing parameterized by Kolmogorov inertial range scalings, and droplet growth. Because th e simulation is performed in a 1D domain, all relevant length scales o f the mixing process can be resolved. For the typical domain size used (20 m) in this study, the growth of approximately 2000 droplets is ex plicitly calculated based on their local environments. Comparisons of computed droplet spectra with spectra obtained from airplane penetrati on exhibit good agreement. Further results showing effects of entraine d CCN, droplet sedimentation and mixing rates on droplet spectral evol ution are provided. (C) 1998 Elsevier Science B.V. All rights reserved .