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Properties of African squall lines inferred from time-lapse satellite imageryAnalysis of 48 h of time-lapse satellite imagery of a family of squall lines in Africa links the phenomena with a characteristic cloud cluster and with a wind field perturbation which is enhanced in passing through an African easterly wave trough. A thin 'arc line' of low-level developing cumulus, a salient feature of the squall lines on the imagery, is shown to occur at the front boundary of the mesoscale/convective scale subsidence. Analysis of the wind field indicates that a squall line is associated with a vorticity center in the mid-level easterly flow which accompanies the mesoscale subsidence which, in turn, contributes to further forced ascent of subcloud air along the front of the squall line into convective towers which merge into an extensive anvil. The squall lines evolved through a life cycle of 6 to 12 h while the larger cloud cluster and wind perturbation lasted over 48 h. The magnitude of the vertical mass exchange suggests that squall-line families contribute significantly to the tropical energy balance.
Document ID
19800045649
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Fortune, M.
(Wisconsin, University Madison, Wis., United States)
Date Acquired
August 10, 2013
Publication Date
February 1, 1980
Publication Information
Publication: Monthly Weather Review
Volume: 108
Subject Category
Meteorology And Climatology
Accession Number
80A29819
Funding Number(s)
CONTRACT_GRANT: NAS5-21798
CONTRACT_GRANT: NOAA-04-3-158-61
CONTRACT_GRANT: NSF GA-41858X
CONTRACT_GRANT: NSF ATM-78-05951
Distribution Limits
Public
Copyright
Other

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