WMOD00293 ‎(2)‎

• Contract/Permit #: 14-06-D-6467
• Project Name: Project No. 15-1371-1113
• Title: A Case Study of the Water Budget of an Orographic Cloud
• Prepared By: L. K. Balick, J. L. Rasmussen
• Date: 5/1/1972
• State: CO
• Country: United States
• Weather Modification - Doc Type: Report

8

water mixing ratios are zero, so that a positive wi - Wo in equation

~

(5) is due to precipitation (P). The condensation computed with data

.

from the windward and leeward radiosondes becomes precipitation (P).

Cloud efficiency is determined by using the results of the water

balance. Efficiency (E) may be defined (Elliot and Hovind, 1964) as

the ratio of the net removal of water to the net condensation.

P
E = C

(6)

Further insight into the problem of cloud efficiency is the evaluation

of the distribution of condensate with temperature since the number of

active ice nuclei and available water vary with temperature. At warm

temperatures (approximately -20oC and above) the cloud is expected to

.

decrease in efficiency due to a relative scarcity of active ice nuclei,

The distribution of condensate with temperature is best determined using

~

the mean temperature of the 8e channels for the mountain crest station.

In summary, then, the method of analysis of the orographic cloud

system is done in three steps: First, the determination of trajectories

of air parcels as they flow over the orographic barrier; second, the

determination of the existance and characteristics of the cloud system;

third, the determination of the atmospheric water balance leading to

the estimate of condensation and precipitation and the efficiency of

the cloud system.

The method described above is for data taken under ideal conditions.

.

The actual locations of radiosondes were less than ideal and were dic-

tated by existing facilities, power and communications. Because of this