The wind and thermodynamic fields associated with eastern
Atlantic cloud clusters are studied using radiosonde data from
the Global Atmospheric Research Program Atlantic Tropical Experiment
(GATE). These data are from the gridded set of winds prepared
by Dr. Katsuyuki Ooyama (AOML-NOAA) and Dr. Jan-Hwa Chu
(SSEC, University of Wisconsin, Madison) using an objective
analysis scheme designed by Dr. Ooyama. Similarly-analysed
thermodynamic data prepared by Dr. Steven Esbensen (Oregon State
University) are also used.
Case studies of the vorticity budget for the 4 September
squall and the 5 September cluster show significant contributions
by all budget terms including the residual, which is interpreted
as the effects of cumulus convection, mesoscale cloud lines, or
other small-scale circulations. The residual is particularly
large in the boundary layer and upper troposphere. The fields
of winds and vorticity budget terms in the upper troposphere of
the two systems are similar. However, at the level of the mid-tropospheric
jet, the small-scale production of vorticity is
significantly different in the two systems.
A technique for compositing clusters using satellite-derived
cloud-top data is applied to GATE data from Phase 3. Vertical
motions within and below the anvils are in accord with previous
studies. Frictionally-induced inflow is found to be of secondary
importance to the development and maintenance of cluster circulations.
The composited vorticity budget residuals are again large
in the boundary layer and upper troposphere.
A large-magnitude asymmetric vorticity couplet observed in
the upper troposphere of individual clusters and in composite
results is examined. Cluster-scale twisting and motions at meso- or
smaller scales are found to produce the couplet, while cluster-scale
divergence is the primary destructive agent. A deceleration
of the strong easterlies at this level produces these couplets.
Possible mesoscale and cumulus sources of this deceleration are
discussed.
Present schemes that parameterize vorticity production by
cumulus convection are found to be inconsistent with similar
schemes that parameterize momentum production. Furthermore, these
vorticity parameterizations cannot describe the production of the
upper-tropospheric couplets discussed above. An alternate parameterization,
formed by taking the curl of the parameterized momentum
source, does qualitatively describe the couplets. / Graduation date: 1984
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29235 |
| Date | 01 June 1983 |
| Creators | Tollerud, Edward I. |
| Contributors | Esbensen, Steven K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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