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

24

In order to cover the entire range of cloud droplet to raindrop, ice crystal

to hailstone sizes of interest with high resolution at small sizes and yet retain a

computationally manageable number of equations the particle mass dimensions will

be represented on a logarithmic scale by means of the following transformation, a

variant of which was first suggested by Berry (1965):

X(J) = 0 for J = 1 and 46
x(J) = x exp [3(J-2)/ J ] for J = 2, ......45
0 0
y(K) = 0 for I = 1 and 46
y(K) = y exp [3(K-2)/J ] for K = 2, . . . . . . .45
o 0
where x = 3.21 E-ll
0
Yo = 9.79 E-9
J = 5.51
0
K = 5.51
0
x(J) = mass of the Jth class interval of liquid drops
y(k) = mass of the Kth class interval of ice particles

(eq. 24)

(eq. 25)

The model can thus cover a range of 2 JJm to 4 mm radius liquid drops in 44

logarithmic J-scale classes and ice particles (assumed spherical) from 13.7 JJm

to 2.81 cm radius in 44 classes logarithmically spaced on a K-scale defined above.

.'

The width of each mass interval is now proportional to the size of the

particles within that interval and the mass resolution for small particles tha~r change

size rapidly under the influence of condensation and sublimation is consequently