RECURRENCE STATISTICS OF CONCENTRATION FLUCTUATIONS IN PLUMES WITHIN A NEAR-NEUTRAL ATMOSPHERIC SURFACE LAYER

Authors
  1. Yee, E.
Corporate Authors
Defence Research Establishment Suffield, Ralston ALTA (CAN)
Abstract
The study examines the statistical properties of the concentration derivative, x, for a dispersing plume in a near-neutrally stratified atmospheric surface layer. Towards this goal, the probability density function (pdf) of x, and the conditional pdf of x given a fixed concentration level, x, distribution with intermittency exponent, q, equal to 0.3 and 3/4, respectively. These results highlight the strong intermittency effect (patchiness) of the small-scale concentration eddy structures in the plume. The distribution of time intervals between successive high peaks in the squared derivative process, x2, is found to be well approximated by a power-law distribution, implying that occurrences of these high peaks are much more clustered than would be predicted by a Poisson or shot-noise process. The results are used to improve models for the joint pdf of x and x', and for the expected number of upcrossings per unit time interval of a fixed concentration level that have been proposed by Kristensen et al. (1989). The predictions of the improved models are in accord with observations, and suggest that the intercorrelation between x and x' must be explicitly incorportaed if good estimates of the upcrossing intensity are to be obtained.
Date of publication
28 Jan 1993
Number of Pages
27
Reprinted from
Boundary-Layer Meteorology, vol 66, 1993, p 127-153
DSTKIM No
94-02899
CANDIS No
141311
Format(s):
Hardcopy;Originator's fiche received by DSIS

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