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| Titel |
Universal dependences between turbulent and mean flow parameters instably and neutrally stratified Planetary Boundary Layers |
| VerfasserIn |
I. N. Esau, S. S. Zilitinkevich |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 13, no. 2 ; Nr. 13, no. 2 (2006-05-08), S.135-144 |
| Datensatznummer |
250011729
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| Publikation (Nr.) |
 copernicus.org/npg-13-135-2006.pdf |
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| Zusammenfassung |
| We consider the resistance law for the planetary boundary layer (PBL) from
the point of view of the similarity theory. In other words, we select the
set of the PBL governing parameters and search for an optimal way to express
through these parameters the geostrophic drag coefficient Cg=u* /Ug and the cross isobaric angle α (where u* is the friction
velocity and Ug is the geostrophic wind speed). By this example, we
demonstrate how to determine the "parameter space" in the most convenient
way, so that make independent the dimensionless numbers representing
co-ordinates in the parameter space, and to avoid (or at least minimise)
artificial self-correlations caused by the appearance of the same factors
(such as u*) in the examined dimensionless combinations (e.g. in Cg=u* /Ug) and in dimensionless numbers composed of the governing
parameters. We also discuss the "completeness" of the parameter space from
the point of view of large-eddy simulation (LES) modeller creating a
database for a specific physical problem. As recognised recently, very large
scatter of data in prior empirical dependencies of Cg and α on
the surface Rossby number Ro=Ug| fz0|-1 (where z0 is
the roughness length) and the stratification characterised by µ was to
a large extent caused by incompactness of the set of the governing
parameters. The most important parameter overlooked in the traditional
approach is the typical value of the Brunt-Väisälä frequency N in
the free atmosphere (immediately above the PBL), which involves, besides Ro
and µ, one more dimensionless number: µN=N/ | f |.
Accordingly, we consider Cg and α as dependent on the three
(rather then two) basic dimensionless numbers (including µN) using
LES database DATABASE64. By these means we determine the form of the
dependencies under consideration in the part of the parameter space
representing typical atmospheric PBLs, and provide analytical expressions
for Cg and α. |
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