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Brownian drift‐diffusion model for evolution of droplet size distributions in turbulent clouds
Author(s) -
McGraw Robert,
Liu Yangang
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl023545
Subject(s) - turbulence , diffusion , drizzle , statistical physics , physics , brownian motion , mechanics , thermodynamics , meteorology , precipitation , quantum mechanics
Effects from turbulence‐induced fluctuations in water vapor saturation on cloud droplet growth are examined using a Brownian diffusion model. The model predicts diffusive broadening of the droplet size distribution, tempered by enhanced evaporation‐induced drift of droplets to smaller size from vapor depletion, and approach to a stationary condition (Weibull distribution) determined by the balance between size‐space diffusion and drift. Monte Carlo simulations of the approach to the stationary limit and of the distribution itself are presented and compared favorably with observation. A key turbulence parameter required by the kinetic potential theory of drizzle formation is estimated using the new results.