Turbulence effects on droplet growth and size distribution in clouds - A review

被引:89
作者
Pinsky, MB [1 ]
Khain, AP [1 ]
机构
[1] Hebrew Univ Jerusalem, IL-91904 Givat Ram, Israel
基金
以色列科学基金会;
关键词
D O I
10.1016/S0021-8502(97)00005-0
中图分类号
TQ [化学工业];
学科分类号
0817 ;
摘要
The paper is focused on inertia effects among drops moving within a turbulent cloud on size distribution evolution and formation of rain. Two related mechanisms are discussed: (1) the occurrence of inertia-induced relative velocities between drops falling within a turbulent flow, and (2) the tendency of inertial drops to concentrate within certain areas of turbulent flow with a corresponding concentration decrease elsewhere. It is shown that these turbulence-induced mechanisms lead to a broadening of the droplet spectrum during the early stages of cloud formation. Turbulence also decreases the minimum size of droplets are able to collide with the smaller ones. Thus, turbulence seems to bridge drop growth by condensation and coagulation. Due to the non-linear nature of the kinetic equation of coalescence, effects of positive fluctuations of drop concentration dominate and lead to a faster droplet spectrum broadening. Turbulence effects for ice particles, especially ice crystals and snowflakes, are expected to be much more pronounced than those demonstrated for water drops, because of a smaller terminal fall velocity of ice particles and a comparably large mass. Large turbulent eddies can concentrate ice crystals within certain areas, where ice crystals concentration will be substantially greater than mean ice crystal concentration. Thus, turbulence can contribute to the formation of high ice crystal concentration observed in mixed-phase clouds. The investigation of turbulence effects in clouds drop evolution is a held currently undergoing very rapid development. Some unsolved problems are discussed. (C) 1997 Published by Elsevier Science Ltd.
引用
收藏
页码:1177 / 1214
页数:38
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