WMOD00289 ‎(2)‎

• Title: Observations and Numerical Simulations of Precipitation Mechanisms in Natural and Seeded Convective Clouds
• Prepared By: Lroen D. Nelson
• Date: 3/1/1979
• State: IL
• Weather Modification - Doc Type: Report

6

of the cloud. While there are many such microphysical Eulerian models in the

literature, the concepts involved in the Eulerian framework are typified by the

work of Nelson (1971) and Silverman and Glass (1973).

Since this model contemplates both detailed microphysics and microphysical-

dynamical interactions between various parts of a cloud, the numerical framework

used herein will be exclusively Eulerian. Chapter II will first describe the physical

equations of the simulated processes and then transform these differential-int(!gral

equations into the framework of Eulerian finite-difference iterative solution algorithms.

The microphysical processes and interactions to be simulated are illustrated schematically

in Figure 1 and have been selected to be a computationally manageable subset of the

larger diagram given by Braham (1968).

Microphysics

Condensation

The condensation growth of droplets containing dissolved hygroscopic: nuclei

is given by Silverman and Kunkel (1970) and Silverman (1972) as:

· dX .
x = - = x(x,y'P ,1') = 4,rrD'Fp H
at v s

I

1 + 20-
....odrTRv

(1 + S) (1 + S/2)

(eq. 1)

[1 + 2~ 1
Ps PdrTRv

(1 +S)!(1 +S/2)R T2KlF'
v

*

-1