Estimation of relative dispersion parameters from atmospheric turbulence spectra

Georgopoulos, Panos G.; Seinfeld, John H.

doi:10.1016/0004-6981(88)90297-1

Cited by 10 publications

(3 citation statements)

References 53 publications

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“…Previous theoretical analysis has been applied to inhomogeneous flows, in particular in the works by de Baas et al (1986), Georgopoulos and Seinfeld (1988), and Degrazia et al (1998), who related dispersion parameters and Lagrangian properties (like the integral time scale) to spectral characteristics of the atmospheric CBL.…”

Section: Introductionmentioning

confidence: 99%

Relating Eulerian and Lagrangian Statistics for the Turbulent Dispersion in the Atmospheric Convective Boundary Layer

Dosio

Arellano

Holtslag

et al. 2005

Journal of the Atmospheric Sciences

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Eulerian and Lagrangian statistics in the atmospheric convective boundary layer (CBL) are studied by means of large eddy simulation (LES). Spectra analysis is performed in both the Eulerian and Lagrangian frameworks, autocorrelations are calculated, and the integral length and time scales are derived. Eulerian statistics are calculated by means of spatial and temporal analysis in order to derive characteristic length and time scales. Taylor's hypothesis of frozen turbulence is investigated, and it is found to be satisfied in the simulated flow.Lagrangian statistics are derived by tracking the trajectories of numerous particles released at different heights in the turbulent flow. The relationship between Lagrangian properties (autocorrelation functions) and dispersion characteristics (particles' displacement) is studied through Taylor's diffusion relationship, with special emphasis on the difference between horizontal and vertical motion. Results show that for the horizontal motion, Taylor's relationship is satisfied. The vertical motion, however, is influenced by the inhomogeneity of the flow and limited by the ground and the capping inversion at the top of the CBL. The Lagrangian autocorrelation function, therefore, does not have an exponential shape, and consequently, the integral time scale is zero. If distinction is made between free and bounded motion, a better agreement between Taylor's relationship and the particles' vertical displacement is found.Relationships between Eulerian and Lagrangian frameworks are analyzed by calculating the ratio ␤ between Lagrangian and Eulerian time scales. Results show that the integral time scales are mainly constant with height for z/z i Ͻ 0.7. In the upper part of the CBL, the capping inversion transforms vertical motion into horizontal motion. As a result, the horizontal time scale increases with height, whereas the vertical one is reduced. Current parameterizations for the ratio between the Eulerian and Lagrangian time scales have been tested against the LES results showing satisfactory agreement at heights z/z i Ͻ 0.7.

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Section: Introductionmentioning

confidence: 99%

Relating Eulerian and Lagrangian Statistics for the Turbulent Dispersion in the Atmospheric Convective Boundary Layer

Dosio

Arellano

Holtslag

et al. 2005

Journal of the Atmospheric Sciences

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show abstract

“…The band-pass filtering that appears in (51) has often been invoked (e.g. Hanna, Briggs & Hosker 1982;Panofsky & Dutton 1984;Georgopoulos & Seinfeld 1988) to explain various aspects of turbulent diffusion. However, this band-pass filtering is directly tied to the single-particle nature of Ogura's equation.…”

Section: Continuous Point Sourcementioning

confidence: 99%

Influence of the sampling time on the kinematics of turbulent diffusion from a continuous source

Eckman

1994

J. Fluid Mech.

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A kinematic description is presented of how turbulent diffusion from a continuous source varies with the sampling time in stationary, homogeneous turbulence. Unlike most previous theories, the sampling is assumed to take place at fixed downstream distances from the source. It is shown that the sampling-time effects depend on two-particle velocity statistics. Thus, time-average diffusion at fixed downstream distances is more akin to relative diffusion than to absolute diffusion. Two simple diffusion models are developed from the kinematic equations. These models are in fairly good agreement with diffusion data obtained both in a wind tunnel and in the field. Moreover, these models have significant practical implications. For example, the models indicate that care must be taken when using band-pass spectral filtering as a paradigm for turbulent diffusion. Also, the models show that the mean flow speed U has an important influence on the sampling-time effects. To account for U properly, diffusion measurements with differing sampling times Λ should be compared using the product UΛ, and not just Λ.

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“…Nevertheless, despite the proliferation of alternatives in research models, the approaches commonly adopted by application-oriented models are rather limited. Indeed, in point source plume and puff models, turbulent dispersion is incorporated in dispersion parameters (a) (24); in grid models it is described by a simple (local) gradient transport approximation that is parameterized with eddy diffusivities (K's); the flux of mass is assumed proportional to the gradient of the mean concentration in a given direction, with K being the proportionality factor. This is often referred to as K-theory of atmospheric dispersion.…”

Section: The Regulatory Modeling Processmentioning

confidence: 99%

Regulatory ozone modeling: status, directions, and research needs.

Georgopoulos

1995

Environ Health Perspect

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The Clean Air Act Amendments (CAAA) of 1990 have established selected comprehensive, three-dimensional, Photochemical Air Quality Simulation Models (PAQSMs) as the required regulatory tools for analyzing the urban and regional problem of high ambient ozone levels across the United States. These models are currently applied to study and establish strategies for meeting the National Ambient Air Quality Standard (NAAQS) for ozone in nonattainment areas; State Implementation Plans (SIPs) resulting from these efforts must be submitted to the U.S. Environmental Protection Agency (U.S. EPA) in November 1994. The following presentation provides an overview and discussion of the regulatory ozone modeling process and its implications. First, the PAQSM-based ozone attainment demonstration process is summarized in the framework of the 1994 SIPs. Then, following a brief overview of the representation of physical and chemical processes in PAQSMs, the essential attributes of standard modeling systems currently in regulatory use are presented in a nonmathematical, self-contained format, intended to provide a basic understanding of both model capabilities and limitations. The types of air quality, emission, and meteorological data needed for applying and evaluating PAQSMs are discussed, as well as the sources, availability, and limitations of existing databases. The issue of evaluating a model's performance in order to accept it as a tool for policy making is discussed, and various methodologies for implementing this objective are summarized. Selected interim results from diagnostic analyses, which are performed as a component of the regulatory ozone modeling process for the Philadelphia-New Jersey region, are also presented to provide some specific examples related to the general issues discussed in this work. Finally, research needs related to a) the evaluation and refinement of regulatory ozone modeling, b) the characterization of uncertainty in photochemical modeling, and c) the improvement of the model-based ozone-attainment demonstration process are presented to identify future directions in this area. -Environ Health Perspect 103(Suppl 2): 107-132 (1995)

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Estimation of relative dispersion parameters from atmospheric turbulence spectra

Cited by 10 publications

References 53 publications

Relating Eulerian and Lagrangian Statistics for the Turbulent Dispersion in the Atmospheric Convective Boundary Layer

Relating Eulerian and Lagrangian Statistics for the Turbulent Dispersion in the Atmospheric Convective Boundary Layer

Influence of the sampling time on the kinematics of turbulent diffusion from a continuous source

Regulatory ozone modeling: status, directions, and research needs.

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