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Computationally efficient expressions for the collision efficiency between electrically charged aerosol particles and cloud droplets
Author(s) -
Tripathi S. N.,
Vishnoi S.,
Kumar S.,
Harrison R. G.
Publication year - 2006
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 - 10.1256/qj.05.125
Subject(s) - aerosol , citation , mathematics , library science , meteorology , operations research , computer science , physics
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 of E , 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 μm, 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 μ m. The parametrization yields values of E well within an order of magnitude of the detailed model's values, from a dataset of 3978 E 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 μ m, and about 96% in the second size range. This parametrization speeds up the calculation of E by a factor of ∼10 3 compared with the original microphysical model, permitting the inclusion of electric charge effects in numerical cloud and climate models. Copyright © 2006 Royal Meteorological Society