Brownian drift-diffusion model for evolution of droplet size distributions in turbulent clouds
نویسندگان
چکیده
[1] 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. Citation: McGraw, R., and Y. Liu (2006), Brownian drift-diffusion model for evolution of droplet size distributions in turbulent clouds, Geophys. Res. Lett., 33, L03802, doi:10.1029/ 2005GL023545.
منابع مشابه
Parameterizations for Clouds and Precipitation Based on the Kinetic Potential Theory for Drizzle Formation
Effects from turbulence-induced fluctuations in water vapor saturation on the growth of cloud droplets are examined using a Brownian-like diffusion model to represent the condensation growth/evaporation of droplets along the coordinate of droplet size. The model predicts a diffusive broadening of the droplet size distribution with time, tempered by enhanced evaporation-induced drift of droplets...
متن کاملKinetic potential and barrier crossing: a model for warm cloud drizzle formation.
The kinetic potential of nucleation theory is used to describe droplet growth processes in a cloud. Drizzle formation is identified as a statistical barrier-crossing phenomenon that transforms cloud droplets to drizzle size with a rate dependent on turbulent diffusion, droplet collection, and size distribution. Steady-state and transient drizzle rates are calculated for typical cloud conditions...
متن کاملA Relaxed Drift Diffusion Model for Phylogenetic Trait Evolution
Understanding the processes that give rise to quantitative measurements associated with molecular sequence data remains an important issue in statistical phylogenetics. Examples of such measurements include geographic coordinates in the context of phylogeography and phenotypic traits in the context of comparative studies. A popular approach is to model the evolution of continuously varying trai...
متن کاملAnalytic Solutions for Evolving Size Distributions of Spherical Crystals or Droplets Undergoing Diffusional Growth in Different Regimes
Motivated by simulations of slow-growing contrail cirrus, the solution of the diffusional growth equations for a population of spherical ice crystals or water droplets is reexamined. For forcing specified by the evolution of the total water content above saturation within a parcel (whether driven by vertical motions, radiative heating, turbulent mixing, etc.) three behavior regimes are identifi...
متن کاملStochastic effects of cloud droplet hydrodynamic interaction in a turbulent flow
The collision efficiencies of small cloud droplets are calculated in a turbulent flow. A flow w velocity field was generated using a model of isotropic turbulence Pinsky, M.B., Khain, A.P., 1995. A model of homogeneous isotropic turbulence flow and its application for simulation of cloud drop tracks. Geophys. Astrophys. Fluid Dyn. 81, 33–55; Pinsky, M.B., Khain, A.P., 1996. x Simulations of dro...
متن کامل