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Cloud Droplets (cloud + droplet)

Distribution by Scientific Domains
Earth and Environmental Science100%

Selected Abstracts

Computationally efficient expressions for the collision efficiency between electrically charged aerosol particles and cloud droplets

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 618 2006
S. N. Tripathi
Abstract A multiple factor parametrization is described to permit the efficient calculation of collision efficiency (E) between electrically charged aerosol particles and neutral cloud droplets in numerical models of cloud and climate. The four-parameter representation summarizes the results obtained from a detailed microphysical model ofE, which accounts for the different forces acting on the aerosol in the path of falling cloud droplets. The parametrization's range of validity is for aerosol particle radii of 0.4 to 10 ,m, aerosol particle densities of 1 to 2.0 g cm,3, aerosol particle charges from neutral to 100 elementary charges and drop radii from 18.55 to 142 , m. The parametrization yields values ofE well within an order of magnitude of the detailed model's values, from a dataset of 3978E values. Of these values 95% have modelled to parametrized ratios between 0.5 and 1.5 for aerosol particle sizes ranging between 0.4 and 2.0 , m, and about 96% in the second size range. This parametrization speeds up the calculation ofE by a factor of ,103 compared with the original microphysical model, permitting the inclusion of electric charge effects in numerical cloud and climate models. Copyright © 2006 Royal Meteorological Society [source]

The role of air turbulence in warm rain initiation

ATMOSPHERIC SCIENCE LETTERS, Issue 1 2009
Lian-Ping Wang
Abstract Quantitative parameterization of turbulent collision of cloud droplets represents a major unsolved problem in cloud physics. Here a hybrid direct simulation tool is used specifically to quantify the turbulent enhancement of the gravitational collision-coalescence. Simulation results show that air turbulence can enhance the collision kernel by an average factor of about 2, and the observed trends are supported by scaling arguments. An impact study using the most realistic collection kernel suggests that cloud turbulence can significantly reduce the time for warm rain initiation. Areas for further development of the hybrid simulation and the impact study are indicated. Copyright © 2009 Royal Meteorological Society [source]