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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

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Vincent J. Schaefer

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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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Vincent J. Schaefer

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Vincent J. Schaefer

Since ancient times man has dreamed of manipulating the weather to his advantage. His efforts to this end have ranged from drawing pictographs, lighting ceremonial fires, participating in rain dances and then during the past twenty-one years in directing his attention toward utilizing certain scientific relationships to initiate physical and chemical reactions in the atmosphere.

There are certain of these reactions which can be demonstrated in both the laboratory and the field. They are spectacular to see, are fairly well understood from the scientific viewpoint and can be used to produce definite and predictable reactions.

There no longer is any question that it is quite feasible to modify supercooled clouds wherever they occur. There is still much uncertainty as to subsequent developments which may occur due to such actions especially in unstable cloud systems. Unlike supercooled fogs and stratus clouds where the seeding results may be photographed and quantitatively measured, these less stable systems involving convection, convergence and divergence of moist and dry air are difficult systems to evaluate.

This paper reviews briefly certain aspects of weather control prior to 1946 and then attempts to provide an accurate historical chronology of the significant advances which occurred during the early period of this new phase of atmospheric science.

The control of the weather within our global atmosphere has been a dream of man for many centuries. In its earliest phases this ambition was limited to the rain needed for a tiny patch of corn or some similar local and immediate need. As man's knowledge of the atmosphere increased and his needs became more urgent and widespread, his approach to such problems were increasingly directed toward a scientific consideration of the possibilities as well as limitations of changing atmospheric processes.

Prior to 1946, all of the proposals advanced toward doing something about modifying atmospheric processes failed to consider the massive nature of the atmosphere and the need to depend on triggering mechanisms to utilize the latent energy which develops from some of the physical reactions and interactions which occur in clear and cloudy skies.

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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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