Intermittency of Turbulence in the Atmospheric Boundary Layer: Scaling Exponents and Stratification Influence |
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Authors: | Email author" target="_blank">J?M?VindelEmail author C?Yagüe |
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Institution: | (1) Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA;(2) NOAA Earth System Research Laboratory, Boulder, CO, USA;(3) U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH, USA;(4) Present address: NorthWest Research Associates, Inc. (Bellevue Division), 25 Eagle Ridge, Lebanon, NH 03766-1900, USA;(5) Naval Postgraduate School, Monterey, CA, USA |
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Abstract: | We show the relationship between the intermittency of turbulence and the type of stratification for different atmospheric
situations during the SABLES98 field campaign. With this objective, we first demonstrate the scaling behaviour of the velocity
structure functions corresponding to these situations; next, we analyze the curvature of the scaling exponents of the velocity
structure functions versus the order of these functions (ζ
p
vs. p), where ζ
p
are the exponents of the power relation for the velocity structure function with respect to the scale. It can be proved that
this curve must be concave, under the assumption that the incompressible approximation does not break down at high Reynolds
numbers. The physical significance of this kind of curvature is that the energy dissipation rate increases as the scale of
the turbulent eddies diminishes (intermittency in the usual sense). However, the constraints imposed by stability, preventing
full development of the turbulence, allow the function ζ
p
versus p to show any type of curvature. In this case, waves of high frequency trapped by the stability, or bursts of turbulence caused
by the breaking up of internal waves, may produce a redistribution of energy throughout the scaling range. Due to this redistribution,
the variation with the scale of the energy dissipation rate may be smaller (decreasing the intermittency) and, even in more
stable situations, this rate may diminish (instead of increasing) as the scale diminishes (convex form of the curve ζ
p
vs. p). |
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Keywords: | |
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