The very stable boundary layer is a region of the atmosphere typified by large
vertical gradients of temperature and momentum. Analysis of very stable atmospheric
flows is complicated by the presence of nonlinear interactions among gravity waves, shear-driven
overturning circulations, two-dimensional vortical modes and intermittent turbulence
in various stages of development. This study examines the horizontal structure of a very
stable atmospheric boundary layer, using data obtained primarily from terrain-following
aircraft flights over central Oklahoma.
Several diagnostic procedures are applied to the aircraft data, including classical and
rotary spectral analysis, principal component analysis, and structure functions. Coherent
structures with sharp boundaries are examined with a new conditional sampling technique
which requires little a priori specification of sampling criteria. Because the flows involve
sharp boundaries, spectral techniques do not provide as much useful information as other
more localized procedures. The edges of the coherent structures are regions of significant
vertical heat transport, a feature not often emphasized in studies of gravity waves and
vortical modes in the stable boundary layer.
The presence of significant turbulence even for large stability has implications for
modelling of the very stable boundary layer. Forecasts of minimum temperature, boundary
layer height, inversion characteristics, and pollutant dispersal are all significantly affected
by turbulent mixing. Many models of the stable boundary layer artificially arrest the
mixing under stable conditions, resulting in, for example, overestimates of nocturnal
cooling. A new parameterization of the stable boundary layer is studied here by
incorporating it into an existing model of the planetary boundary layer. The model is then
run with one-dimensional sensitivity tests for an idealized atmosphere and with data from
Wangara day 33. A simulation over snow cover is also examined. The tests substantiate
the role of vertical mixing in ameliorating nocturnal cooling. An additional improvement is
a more realistic boundary layer height for moderate wind speeds. / Graduation date: 1988
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29289 |
| Date | 02 October 1987 |
| Creators | Ruscher, Paul Harold |
| Contributors | Mahrt, Larry |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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