Photographic and Radar Study of the Stormfury 5 August 1965 Seeded Cloud

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  • 1 Environmental Science Services Administration, Silver Spring, Md.
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Abstract

In the summer of 1965, a series of tropical cumulus cloud experiments was carried out by Project Stormfury, a joint program of the U. S. Navy and Environmental Science Services Administration. Of twelve clouds seeded with tops colder than −5C, eight grew an average of 10,600 ft following seeding. This is a case study of one of these eight clouds; it was seeded at 25,000 ft (absolute altitude) and grew to about 36,000 ft.

Four instrumented aircraft penetrated the cloud in a stack, at levels from cloud base to about 20,000 ft. A heavily radar equipped “Command” plane controlled the experiment, circling the cloud at a distance of about 25 mi. This paper documents the radar and photographic history of the cloud, mainly as determined from the command aircraft. It is intended to aid in interpretation of the cloud physics measurements provided by the penetrating aircraft, particularly that of the Naval Research Laboratory. The N.R.L. aircraft made repeated traverses through the cloud at 18,000 ft (absolute altitude; 17,000 ft pressure altitude) in the temperature range −3 to −5C. It measured temperature, humidity, and hydrometeor structure, once before and several times after seeding. Conversion from largely water to largely ice was observed in a portion of the cloud together with some interesting temperature increases. This study attempts to relate the seeding effects and internal physical changes to the overall dynamic processes as deduced from radar and photography.

Abstract

In the summer of 1965, a series of tropical cumulus cloud experiments was carried out by Project Stormfury, a joint program of the U. S. Navy and Environmental Science Services Administration. Of twelve clouds seeded with tops colder than −5C, eight grew an average of 10,600 ft following seeding. This is a case study of one of these eight clouds; it was seeded at 25,000 ft (absolute altitude) and grew to about 36,000 ft.

Four instrumented aircraft penetrated the cloud in a stack, at levels from cloud base to about 20,000 ft. A heavily radar equipped “Command” plane controlled the experiment, circling the cloud at a distance of about 25 mi. This paper documents the radar and photographic history of the cloud, mainly as determined from the command aircraft. It is intended to aid in interpretation of the cloud physics measurements provided by the penetrating aircraft, particularly that of the Naval Research Laboratory. The N.R.L. aircraft made repeated traverses through the cloud at 18,000 ft (absolute altitude; 17,000 ft pressure altitude) in the temperature range −3 to −5C. It measured temperature, humidity, and hydrometeor structure, once before and several times after seeding. Conversion from largely water to largely ice was observed in a portion of the cloud together with some interesting temperature increases. This study attempts to relate the seeding effects and internal physical changes to the overall dynamic processes as deduced from radar and photography.

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