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C. B. Moore
and
B. Vonnegut

Abstract

No abstract available.

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H. H. Jonsson
and
B. Vonnegut

Abstract

Apparatus has been designed and constructed for real-time measurements of the electrical conductivity of rainwater. It utilizes a spinning disk that centrifuges and collects the rainwater failing on it A micro conductivity cell is employed, which consists only of electrodes, and needs no embodiment to sustain the rain sample during measurement. Instead the liquid is retained between the electrodes by its own surface tension. Only the order of a microliter of rain water is needed to obtain a inclement. The system's response time is about a second. Test runs during thunderstorms and frontal rains reveal that variations in conductivity by up to a factor of 5 occur during a storm event. Maximum conductivities of up to 160 μS cm−1 usually occurred at the beginning of the storms. In one thunderstorm rainwater conductivity as low as 5 μS cm−1 was measured for a duration of a few minutes.

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Ronald B. Standler
and
Bednard Vonnegut

Abstract

Estimates based on information in medical and meteorological literature indicate that AgI in the air and in precipitation does not pose a danger to people in the target area. Although the concentration of AgI near the generator is much larger, interviews with operators who have been seeding on a large scale for many years fail to disclose any instances of ill effects from AgI.

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H. F. Eden
and
B. Vonnegut

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R. F. Griffiths
and
B. Vonnegut

Abstract

No abstract available.

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A. K. Kamra
and
B. Vonnegut

Abstract

A laboratory experiment has been performed to study the relative effect of aerodynamic and electrical forces an small electrically conducting particles of radii 100–200 μ colliding with a particle of 2 mm radius suspended in an upward moving vertical air stream of a wind tunnel and placed in a vertical polarizing electric field. It has been observed, in a low electric field, that the smaller particles collide and move up with the air stream. However, as the electric field is increased, the smaller particles start coming down, after the collision, against the air stream. The electric field required for this change of direction for different particle sizes is higher for the larger angles of collision. When these results are applied to thunderstorms with high electric fields, it is shown that the electrical forces on the charged cloud particles must be taken into account in any consideration of the gravitational separation of charges. Our experimental results indicate that in high electric fields these electric forces can limit and even oppose the further separation of charges.

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Bernard Vonnegut
and
Charles B. Moore

Apparatus is described for measuring and recording the atmospheric potential gradient from an aircraft. It consists of two radioactive probes connected through an electromechanical coupling device to a conventional electrometer and recorder.

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H. H. Jonsson
and
B. Vonnegut

Abstract

Experiments are described on the behavior of a wind vane that is constructed in such a way that it is forced to oscillate about the wind direction. The forcing is accomplished by allowing the upwind edge of the vane's fin to jibe back and forth between two detents. The frequency of the oscillation is found to be directly proportional to the wind speed. For a given wind speed, the frequency varies with the square root of the fin area and the inverse square root of the anemometer's moment of inertia. The response time of the device is proportional to the inverse of the frequency.

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J. J. Jones
,
C. Grotbeck
, and
B. Vonnegut

Abstract

A simple instrument that detects ice particles has been developed for use in airplane studies of thunderstorms. Although sophisticated instruments are available for imaging atmospheric ice particles, the spatial resolution of the particle concentration determined from their data is limited by the small size of the sample area. The ice detector described here provides a real-time indication of the presence of ice crystals within and in the vicinity of clouds, and provides an approximate measure of their concentrations with excellent spatial resolution. This device, which is simple and inexpensive, has been flown for five summers in New Mexico thunderstorms.

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B. Vonnegut
,
O. H. Vaughan Jr.
, and
M. Brook

Photographs have been taken at night from an airplane at an altitude of 20 km looking directly down on the tops of thunderclouds illuminated by lightning. The hard, cauliflower-like appearance of the clouds gives evidence that strong convective activity is present. In one case a well-organized system of convective structures is evident whose deepest folds, apparently caused by downdrafts, are estimated to extend into the cloud for depths of as much as several kilometers. Often the whole cloud top, approximately 10 km across, is diffusely illuminated by lightning that is occurring lower in the cloud. In most of these cases no lightning channels can be seen, but occasionally a few segments of channels are visible bridging the folds between the convective protuberances. A few photographs show thin, weak, lightning channels that come out of the top of the cloud, proceed horizontally for several hundred meters, and then terminate in the clear air above the cloud. When such channels can be seen, the background is usually quite dark, indicating that not much lightning activity is taking place elsewhere in the cloud at that time. In one unusual photograph the only evidence of luminous activity is a small region of diffuse illumination no larger than a few hundred meters in diameter. The occurrence of such small, weak discharges is evidence that small pockets of high-density space charge can accumulate within the cloud. The lightning flashes that emerge from the tops of tall, penetrative cells may introduce oxides of nitrogen and other chemical by-products directly into the stratosphere.

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