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Cirrus Uncinus Generating Cells and the Evolution of Cirriform Clouds. Part II: The Structure and Circulations of the Cirrus Uncinus Generating Head

1975; American Meteorological Society; Volume: 32; Issue: 4 Linguagem: Inglês

10.1175/1520-0469(1975)032 2.0.co;2

1520-0469

Andrew J. Heymsfield,

Particle Dynamics in Fluid Flows

Abstract The structure and circulations of the cirrus uncinus generating head were determined from aircraft measurements of the temperatures, horizontal wind velocities and particle spectra at different altitudes. Stable layers were found to exist directly above and below the head. The head was found to exist in a region with a dry adiabatic lapse rate. Waves were observed in the stable layer below the head. The head was found to he divided into two regions in active cirrus uncinus. The upshear part of the head is the updraft region, and the downshear part the downdraft region. A region containing almost no crystals was found to separate the up- and downdraft regions. This “hole” was typically 150 m across. The vertical velocities in cirrus uncinus were determined from aircraft and Doppler radar measurements. Typical vertical velocities were estimated to range from 100–200 cm s−1 from aircraft particle measurements, and determined from Doppler radar measurements to range from 120–180 cm s s−1 Typical down...