The Comparison Of Methods For Droplets Growth By Condensation

For the droplets growth of condensation, it is resolved by bin-resolved microphysics and parameterization in the current cloud model. Theory of the droplet spectrum by condensation is that the droplet spectrum by condensation can only get narrower. This article use the theory of cloud drop growth by condensation. By simulating, the two kinds of calculation method of cloud droplets growth by condensation is compared with analytical solution. We also simulate a triple-moment parameterization scheme. Our simulating results show that:1 The analytic solution of droplet spectrum matchs the theory of droplet growth process of condensation.Small drops grow fast, but large drops grow slowly. The droplet spectrum by condensation only grow into the narrow spectrum. After 30 minutes,there are not cloud droplets which diameters are greater than 40 micron; 2 Because the numerical diffusion, The droplet spectrum (120 bin) of bin-resolved microphysics does not get narrow. The droplet spectrum(2000 bin) gradually get narrow; 3 The droplet spectrum of Milbrandt Two-moment scheme appears wider. Because in the Milbrandt Two-moment scheme, the slope parameter(a) is constant, the slope of the spectrum od cloud is not changged;4 The simulation of droplets spectrum by condensation of the triple-moment parameterization scheme(Clark scheme) is more like analytical solution than Milbrandt Two-moment scheme.In the triple-moment parameterization scheme, there are three parameters(No, α,λ),but there are two predictand. The prognostic equations are not closed. In clark scheme, because of λ=α/R, the prognostic equations are closed.Therefore, Clark sheme can be used to improve the simulation of cloud droplets spectrum by condensation of general parameterized method at present.