WMOD00317

• Contract/Permit #: 14-06-D-6999
• Project Name: CAWRP
• Title: Cascades Atmosphere Water Resources Program - Volume I
• Prepared For: US Department of the Interior Bureau of Reclaimation
• Date: 7/1/1970
• Weather Modification - Doc Type: Report

- 72 -

3.3.3

Critical Concentrations of Ice Particles

The critical concentration N of ice particles is defined as that
- c
concentration for which the total mass growth of the ice particles by

deposition from the vapor phase is equal to the r'ate Cy;': supply of water vapor.

Therefore,

1H
N ......:.. =
c Jt

c
....E. (Y - Y )w
L d m

(3.70)

where, c is the specific heat of dry air at const...r:lt pressure, Yd and Y the
P m
temperature lapse rat~s of cry a5~ and moist air respectively, and w the

updraft velocity of the air. In the ctise of a pla"te-like ice p;:J.rticle ~~

is given by eqn. (3.67), and eqn. (3.70) beccmes

N =
c

c (Yd - Y );..
P Tl!-
8LrGS.
1

(3.71)

3.3.4

Terminal Velocities and Masses of Ice P~rticles

Th,e functional dependence of the mass H and the te~inal fall speed V c

of an ice particle on the radius I' are assumed to be of the form

M =

b
a(r)

(3.72~

and,

V =
c

d
c(r)

(3.73)

1--
,1-
I
l
l
I
I-
I
I
I
I-
I
I
I
I
I
I
I
I