WMOD00298

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

4.1 Schematic diagram of the mechanisms by which ice crystals
can form in a cooling cloud parcel. "Ice particles are
indicated by shading and the various symbols describing
rates and nucleating fractions are discussed in the text.

4.2 Schematic of the thermodynamic history of a parcel between
ice and water saturation (a) during expansion-cooling,
representing a pathway over which deposition nucleation can
be measured. Computation of the nucleation rate at two
points is shown in (b).

4.3 Dry particle size versus equivalent haze particle size of
AgI-AgCl-4NaCl aerosols at water saturation, computed
empirically as described in the text.

4.4 Size distribution of AgI-AgCl aerosols from the CSU standard
generator, determined by scanning electron microscopy.

4.5 Size distribution of AgI-AgCl-4NaCl aerosols produced by
the CSU standard generator, determined by electrostatic
classification. The double hatched distribution gives the
raw measurements, while the single hatched area is the
distribution after correction for charging efficiency and
multiple charging effects (see text).

5.1 Ice formation with respect to cloud formation point in two
experiments used in the analysis of deposition nucleation
by AgI-AgC1 aerosols. The raw ( )and deconvo1uted ( ) ice
-1
fractions nucleated (s ) versus temperature are shown in
part (a). Cloud droplet concentrations ( ) are also
indicated. The deconvo1uted cumulative ice fractions
nucleated are compared versus ice supersaturation in part
(b). Cloud formation points are indicated by arrows.

5.2 Summary of the thermodynamic history of data records
indicating ice formation before cloud point in a number of
experiments used to quantify deposition nucleation for AgI-
AgCl (a) and AgI-AgCl-4NaC1 aerosols.

5.3 Active site density by deposition versus supersaturation
with respect to ice for AgI-AgCl aerosols. A power law fit
to the data using (5.1) is indicated. Data points are coded
to be lOO times the aerosol diameter in microns.

5.4 Fractions of AgI-AgCl aerosols effective by deposition for
AgI-AgCl aerosols. Points are coded as in Figure 5.3, and
the lines through the crosses indicate values computed for
0.07 and 0.03~m diameter sizes using (5.1).

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