WMOD00310

• Title: Cloud Physics Investigations - University of Wyoming - 1977-1981
• Date: 11/1/1982
• State: WY
• Weather Modification - Doc Type: Report

because most droplets would evaporate partially but only a few would

disappear. Also, the size spectrum would shift toward smaller sizes.

The HIPLEX-l case studies provided ample support for the ;.

predictions of inhomogeneous mixing. Examples of the high correlation

./

between droplet concentration and liquid water content are shown in

Fig. 2.8, and were also discussed by Cooper and Rodi (1982). The shapes

of the droplet spectra also support the predictions of inhomogeneous

mixing. Fig. 2.9 shows some examples of spectra observed at adjacent

locations during passes through the HIPLEX-l clouds. These spectra were

generally measured near the -aoc level, and were within 0.5 kIn of the

cloud top. The dominant variation in these spectra is consistent with

the application of a scale factor to the size spectrum. The shape of

the spectrum exhibited little variation on a given pass, even when the

liquid water content and number concentration varied by a factor of two

or more.

Al though these measurements provide strong support for the

inhomogenei ty of the mixing process, the evolution of the droplet

spectrum still poses an interesting puzzle. As shown in Fig. 2.10, the

change wi th time was a general broadening, often accompanied by the

production of small droplets. The spectra were consistent on any single

pass, but the spectra observed on repeated passes differed much more

than did the nearby spectra from any single pass.

These observations suggest that evaporation and initial mixing

alone do not broaden the spectrum, but (at least in some cases)

proceed through processes that are highly inhomogeneous.

However,

substantial broadening does occur with time, and in some cases bimodal

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