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

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- 77 -

The liquid water content X is also calculated using the parcel method.
He have
c
X = -E. (Yd - Ym) (z - H ) (z < H ) }
L c 0 c
c (3.78)
X = X + -E. (Y - Y ) (z - z ) (z > H )
0 L d m 0 0 c

3.4.3 Equations for Crystal Growth and Displacement
The positions and sizes of the ice particles are calculated at time

increments t\t~ The wind, temperature, and liquid water content when the

particle is at [x(t), z{t)] are also determined. These values are assumed

constant over the path of the particle during the next time increment. The

critical concentration of ice particles is calculated to determine the growth
mode of the particle over the next time increment. Then the appropriate growth
equation and the mass-radius and velocity-radius relations may be manipulated
to obtain the particle position and radius at time (t + t\t). The successive
positions of the ice particles are calculated from the starting position
until the particle reaches ground level. The program output consists of these
successive positions, the particle size and precipitation rate at ground level,
and the particle size.and winds, temperature, and liquid water content at
positions where the mode of growth of the particle changes.
(a) Glaciated Condition (N > N )
o c

Under glaciated conditions the ice particles grow solely by diffusion, and

their growth rate is limited by the rate of supply of water vapor due to the

adiabatic lifting of the surrounding air. Thus