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A model of the development of the droplet spectrum in a growing cumulus turret
Author(s) -
Hill T. A.,
Choularton T. W.
Publication year - 1986
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711247214
Subject(s) - entrainment (biomusicology) , turret , buoyancy , cloud base , mechanics , cloud computing , meteorology , environmental science , momentum (technical analysis) , broad spectrum , atmospheric sciences , physics , chemistry , engineering , computer science , mechanical engineering , finance , rhythm , acoustics , combinatorial chemistry , economics , operating system
A model is presented which describes the growth of the droplet spectrum in a growing cumulus turret in which the vertical velocities are determined by buoyancy forces. It is found that if the entrainment of dry air occurs continuously and homogeneously across the cloud then no enhanced growth of the largest droplets in the spectrum occurs unless the environment is assumed to be saturated with a lower concentration of CCN than in the air entering cloud base. This model is used as the basis for a comparison between recent cloud microphysical models, with a view to resolving some of the discrepancies in the results associated with them. Emphasis is placed on the propensity of a particular formulation to produce large droplets. If entrainment is allowed to occur discontinuously and non‐uniformly across the cloud then substantial enhanced growth can occur, in agreement with observations, provided that each part of the cloud experiences several distinct entrainment events. It is found that a highly buoyant turret is required to provide the momentum needed for the continual ascent of these regions.