A Concentration pdf for the Relative Dispersion of a Contaminant Plume in the Atmosphere

Munro, R. G.; Chatwin, P. C.; Mole, N.

doi:10.1023/a:1021209622648

Cited by 19 publications

(25 citation statements)

References 22 publications

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“…11b)]. As expected, the former type is the most probable in the plume centerline, as shown by Munro et al (2003a), because the relative concentration in the mean plume position is very often different than zero. On the contrary, far from the centerline small concentrations are more probable, and consequently the PDF shows an exponential shape.…”

Section: ) Pdf Of Relative Concentrationsupporting

confidence: 72%

“…To distinguish and quantify the different contributions of large-scale (meandering) and small-scale motion (relative diffusion) to the evolution of a dispersing plume, it is useful to calculate second-and third-order moments in two different coordinate systems (e.g., Munro et al 2003b). By analyzing dispersion in an absolute framework, that is, in a coordinate system relative to a fixed point (e.g., the source location), the statistical properties are influenced by the full spectrum of turbulent eddies.…”

Section: Introductionmentioning

confidence: 99%

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Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Dosio

Arellano

2006

Journal of the Atmospheric Sciences

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The influence of the different scales of turbulent motion on plume dispersion in the atmospheric convective boundary layer (CBL) is studied by means of a large-eddy simulation (LES). In particular, the large-scale (meandering) and small-scale (relative diffusion) contributions are separated by analyzing dispersion in two reference systems: the absolute (fixed) coordinate system and the coordinate system relative to the plume's instantaneous center of mass. In the relative coordinate system, the (vertically) inhomogeneous meandering motion is removed, and only the small-scale, homogeneous turbulent motion contributes to the dispersion process.First, mean plume position, dispersion parameters (variance), and skewness of the plume position are discussed. The analysis of the third-order moments shows how the structure and the symmetry of scalar distribution are affected with respect to the turbulent characteristics of the CBL (inhomogeneity of the large-scale vertical motion) and the presence of the boundary conditions (surface and top of the CBL). In fact, the reflection of the plume by the CBL boundaries generates the presence of nonlinear crosscorrelation terms in the balance equation for the third-order moments of the plume position. As a result, the third-order moment of the absolute position is not balanced by the sum of the third-order moments of the meandering and relative plume position.Second, mean concentration and concentration fluctuations are calculated and discussed in both coordinate systems. The intensity of relative concentration fluctuation i cr , which quantifies the internal (in plume) mixing, is explicitly calculated. Based on these results, a parameterization for the probability distribution function (PDF) of the relative concentration is proposed, showing very good agreement with the LES results. Finally, the validity of Gifford's formula, which relates the absolute concentration's high-order moments to the relative concentration and the PDF of the plume centerline, is studied. It is found that due to the presence of the CBL boundaries, Gifford's formula is not able to reproduce correctly the value of the absolute mean concentration near the ground. This result is analyzed by showing that, when the plume is reflected by the CBL boundaries, the instantaneous relative plume width zЈ 2 r (t) departs from its mean value 2 r . By introducing the skewness of the relative plume position into a parameterization for the relative mean concentration, the results for the calculated mean concentration are improved.

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Section: ) Pdf Of Relative Concentrationsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Dosio

Arellano

2006

Journal of the Atmospheric Sciences

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“…The information of the absolute concentration requires an independent calibration, which is not available from aerosol backscatter alone. The raw data from the present experiment can be compared to, for instance, those by Mylne and Mason (1991), Zimmerman and Chatwin (1995) and Munro et al (2003a). The line-of-sight averaging over the effective 1.5 m spatial extent of the Lidar pulse results here in less spiky signals in comparison.…”

Section: Observationsmentioning

confidence: 89%

Concentration Fluctuations in Smoke Plumes Released Near the Ground

Jørgensen

Mikkelsen

Pécseli

2010

Boundary-Layer Meteorol

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Near-ground artificial cloud releases in the turbulent atmospheric boundary layer were investigated experimentally by Lidar measurement techniques. Simple scaling relations between the average concentration and the lowest order moments are suggested by simple analytical models, and the experimental results are tested against these hypotheses. We find strong evidence for a simple scaling of the standard deviation, skewness and kurtosis with the average concentrations at the downwind distances observed in our experiments. Near-ground concentration fluctuations in fixed as well as moving frames of references are investigated. The scaling is supported by data from several experimental sites and different atmospheric stability conditions. One conclusion of the study is that relatively accurate estimates for the standard deviation, skewness and kurtosis can be obtained for the concentration fluctuations, given a reliable estimate of the space-time varying average concentration field.

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“…If we turn away from our objective of naturally occurring scalars over large area sources, and towards contaminant plumes from point sources, we find that the use of third-order and higher-order moments and the assumption of bounded PDFs is more common (Yee et al 2006;Chatwin et al 1995;Munro et al 2003;Schopflocher et al 2007). This may be attributed to two causes: first, it is crucial in the estimation of exceedance probabilities, e.g.…”

Section: State Of Knowledgementioning

confidence: 99%

“…by superposition of several weighted unimodal distributions to a composite (e.g., Effelsberg and Peters 1983;Munro et al 2003;Wendland et al 2005). Overall, however, the beta distribution reliably allows a fairly qualified quick view of the general PDF shape based on the first four moments only.…”

Section: Relation Of Sample Higher Order Moments To Sample Extremamentioning

confidence: 99%

Boundedness of Turbulent Temperature Probability Distributions, and their Relation to the Vertical Profile in the Convective Boundary Layer

Graf

Schüttemeyer

Geiss

et al. 2009

Boundary-Layer Meteorol

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Higher-order moments, minima and maxima of turbulent temperature and water vapour mixing ratio probability density functions measured with an eddy-covariance system near the ground were related to each other and to vertical boundary-layer profiles of the same scalars obtained through airborne soundings. The dependence of kurtosis on squared skewness showed a kurtosis intercept below the Gaussian expectation, suggesting a compression of the probability density function by the presence of natural boundaries. This hypothesis was corroborated by comparing actual minima and maxima of turbulent fluctuations to estimates obtained from the first four sample moments by fitting a four-parameter beta distribution. The most sharply defined boundaries were found for the minima of temperature datasets during the day, indicating that negative temperature fluctuations at the sensor are limited by the availability of lower temperatures in the boundary layer. By comparison to vertical profiles, it could be verified that the turbulent minimum of temperature near the ground is close to the minimum of potential temperature in the boundary layer. The turbulent minimum of water vapour mixing ratio was found to be equal to the mixing ratio at a height above the minimum of the temperature profile. This height roughly agrees with the top of the non-local A. Graf (B) · M. Herbst · H. Vereecken Agrosphere (ICG-4), 123 460 A. Graf et al.unstable domain according to bulk Richardson number profiles. We conclude that turbulence statistics measured near the surface cannot be solely explained by local effects, but contain information about the whole boundary layer including the entrainment zone.

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A Concentration pdf for the Relative Dispersion of a Contaminant Plume in the Atmosphere

Cited by 19 publications

References 22 publications

Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Statistics of Absolute and Relative Dispersion in the Atmospheric Convective Boundary Layer: A Large-Eddy Simulation Study

Concentration Fluctuations in Smoke Plumes Released Near the Ground

Boundedness of Turbulent Temperature Probability Distributions, and their Relation to the Vertical Profile in the Convective Boundary Layer

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