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Vincent J. Schaefer

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Vincent J. Schaefer

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Vincent J. Schaefer

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Vincent J. Schaefer
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Vincent J. Schaefer
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Vincent J. Schaefer
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Vincent J. Schaefer

An exploration of the diurnal variations in the microclimate of a forested mountain in northern Idaho was made during a 36 hour period toward the end of a prolonged period of cloudless weather. Measurements were made from the mobile weather observatory developed jointly by the University of Washington, U. S. Forest Service and the Munitalp Foundation. A 4 meter mast mounted so it rode six feet ahead of the vehicle contained sensing elements at the ½, 2 and 3½ meter positions. Temperature and dew point were recorded on an eight channel recorder which completed its cycle every 32 seconds. Exploratory runs were made during which the observatory stopped at each 500 foot gain in altitude and at several additional stations in between. A study of the data showed, however, that the response time of the aspirated temperature and dew point sensing elements was so rapid that pauses were not necessary if the vehicle moved in the speed range of 6 to 10 mph.

Large differences were noted between day and night and north and south slopes. The so-called “thermal belt” was sharply defined and the drainage winds, stable and unstable air regions and the movement of moisture from the upper slopes into the valleys by drainage winds down the stream valley were nicely indicated by this dynamic study.

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Vincent J. Schaefer

The basic laboratory experiment in which a supercooled cloud may be seeded and converted to ice crystals is described in considerable detail. Such information is given as type and preparation of the cold chamber, light sources which are effective for different purposes, methods to follow in forming supercooled clouds, and procedures to follow in seeding them.

The transition temperature at which ice crystals form spontaneously is given as − 39°C ± 0.1°C as the result of a recent study. A simple replica technique for preserving the exact structure of the crystals in plastic is described.

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Vincent J. Schaefer

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Vincent J. Schaefer

Abstract

A very small electrically conducting wire or fiber, when charged to about 3000 V dc in a cold chamber with its air supersaturated with respect to ice, produces a dense streamer of tiny, free floating ice crystals in the temperature range −8 to −15C. Some of the crystals show evidence their structure is modified by the electrical field or that coagulation with other crystals or cloud droplets occurs.

That similar effects occur in natural clouds is suggested by the occurrence of certain crystal types in snow storms.

The concentration of crystals which form in the cold chamber could, if the phenomenon occurs in convective clouds, readily explain the chain reaction mechanism which must occur when such clouds are rapidly glaciated.

The suggestion is made that studies of the role played by tiny fibers in clouds should be initiated.

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