WMOD00298

• Title: Quantifying Ice Nucleation by Silver Iodide Aerosols
• Date: 5/1/1990
• State: CO
• Weather Modification - Doc Type: Report

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achieved (using an air preconditioning system and forced cooling of the

inner liner). Wall temperature effects (heat transfer) are mimimized by

cooling the inner liner to match the calculated mean air temperature.

This is accomplished by circulating fluid (LEXSOL) through spiral-wound

copper tubing which is soldered to the copper liner. Large compressors

are used to cool the fluid, and the rate of introduction of the cooled

fluid to the circulating fluid loop is regulated by a computer-

controlled digital valve. A software program was developed to use

measured versus programmed wall temperatures in time to empirically

drive adjustments to valve position, as needed. A homogeneous working

volume, free from large thermal or vapor gradients is thus made to

simulate a wide range of air parcel and cloud conditions. An example of

a particular experimental versus programmed ascent profile is shown in

Figure 3.2. The usable working ranges and system tolerances of the
dynamic cloud chamber are:

temperature +40oC to -55OC :t 0.2OC
pressure 90kpa to < lOkpa :t 0.5mb
relative humidity O.l% to > lOO%
simulated vertical velocity 0.2 m -1 to 20 m -1
s s

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Cloud droplet sizes and concentrations are measured with a

Particle Measuring Systems (PMS) FSSP-100. A small funnel shaped glass

tube protrudes 10 cm into the cloud volume and draws cloud air into the

FSSP. The sample inlet necks down to 0.65 mm, and with a sampling rate
-1 -1
of 0.4 L min , the flow accelerates to 20 m s . This stream is

combined with an isokinetic sheath flow and is directed through the