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Magnitude and frequency of wind speed shears and associated downdraftsData are presented indicating the frequency of occurrence of wind shear and downdrafts together with information on the simultaneous occurrence of these two phenomena. High resolution wind profile measurements recorded at a 150 meter ground winds tower facility were used for the analysis. From instantaneous measurements during horizontal wind speeds of gale-force and below intensity, vertical motion at the 10, 60, and 150 m levels was approximately 60 percent downward and 40 percent upward. At the 18 level the percentages were reversed. Updraft maxima were an order of magnitude or two greater than downdrafts at all levels. Frequency of vertical motion or = 9.7 kts for a year at four levels was 338 occurrences upward and 274 downward. Approximately 90 percent of these updrafts occurred at the 18 m level almost equally during summer and winter, and 65 percent of the downdrafts were at the 150 m level during summer.
Document ID
19810010529
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Alexander, M. B.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Campbell, C. W.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 11, 2013
Publication Date
March 1, 1981
Publication Information
Publication: NASA. Langley Research Center The 1980 Aircraft Safety and Operating Probl., Pt. 1
Subject Category
Air Transportation And Safety
Accession Number
81N19055
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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