Influence of diurnal and inertial boundary-layer oscillations on long-range dispersion

Abstract Coupled meteorological and Lagrangian particle models are used to examine horizontal dispersion over one to two diurnal cycles. Seven numerical experiments were run in which different portions of the atmospheric energy spectrum were included or excluded in the simulation of releases of a non-buoyant pollutant from an elevated point source. The results of the experiments indicate that vertical shear in the horizontal wind produced by diurnal and/or inertial oscillations in conjunction with or followed by vertical PBL mixing are capable of maintaining plume growth rates which are nearly linear with diffusion times up to 48 h. The model results agree reasonably well with long-range dispersion observations of an isolated smelter plume made in Australia. Periods of accelerating diffusion found in the simulations have also been indicated in observations. These accelerating diffusion periods in the simulations are due to time-dependent shear in the planetary boundary layer at night. Shear due to synoptic-scale horizontal temperature gradients was also found to have a significant impact on the modeled plume growth rates.

[1]  Frans T. M. Nieuwstadt,et al.  An application of the Langevin equation for inhomogeneous conditions to dispersion in a convective boundary layer , 1986 .

[2]  P. A. Sheppard,et al.  Atmospheric Diffusion , 1962, Nature.

[3]  E. Bigg,et al.  Measurement of the dispersion of a smoke plume at large distances from the source , 1978 .

[4]  Roger A. Pielke,et al.  A Three-Dimensional Numerical Model of the Sea Breezes Over South Florida , 1974 .

[5]  F. B. Smith.  Horizontal diffusion in the atmosphere: A lagrangian dynamical theory , 1983 .

[6]  J. Garratt,et al.  The inland boundary layer at low latitudes: II Sea-breeze influences , 1985 .

[7]  R. W. James.  A NOTE ON THE VERTICAL STRUCTURE OF A TYPHOON , 1951 .

[8]  A. Blackadar,et al.  High resolution models of the planetary boundary layer , 1979 .

[9]  J. Deardorff,et al.  Three-dimensional numerical study of turbulence in an entraining mixed layer , 1974 .

[10]  F. A. Gifford,et al.  Horizontal diffusion in the atmosphere: A Lagrangian-dynamical theory , 1982 .

[11]  John C. Wyngaard,et al.  Turbulence in the Evolving Stable Boundary Layer , 1979 .

[12]  J. Deardorff.  Three-dimensional numerical study of the height and mean structure of a heated planetary boundary layer , 1974 .

[13]  J. Kaimal,et al.  Turbulence Structure in the Convective Boundary Layer , 1976 .

[14]  Steven R. Hanna,et al.  A Method of Estimating Vertical Eddy Transport in the Planetary Boundary Layer Using Characteristics of the Vertical Velocity Spectrum. , 1968 .

[15]  K. S. Gage,et al.  Evidence far a k−5/3 Law Inertial Range in Mesoscale Two-Dimensional Turbulence , 1979 .

[16]  P. Durbin.  Comments on papers by Wilson et al. (1981) and Legg and Raupach (1982) , 1984 .

[17]  I. V. D. Hoven.  POWER SPECTRUM OF HORIZONTAL WIND SPEED IN THE FREQUENCY RANGE FROM 0.0007 TO 900 CYCLES PER HOUR , 1957 .

[18]  J. Kaimal,et al.  Spectral Characteristics of Surface-Layer Turbulence , 1972 .

[19]  Steven R. Hanna.  Some Statistics of Lagrangian and Eulerian Wind Fluctuations. , 1979 .

[20]  Anne J. Ley.  A random walk simulation of two-dimensional turbulent diffusion in the neutral surface layer , 1982 .

[21]  D. Thomson,et al.  Random walk modelling of diffusion in inhomogeneous turbulence , 1984 .

[22]  G. W. Thurtell,et al.  Numerical simulation of particle trajectories in inhomogeneous turbulence, I: Systems with constant turbulent velocity scale , 1981 .

[23]  D. Lenschow,et al.  The characteristics of turbulent velocity components in the surface layer under convective conditions , 1977 .

[24]  R H Varey,et al.  Atmospheric Diffusion (3rd edn) , 1984 .

[25]  F. B. Smith.  Conditioned particle motion in a homogeneous turbulent field , 1968 .

[26]  R. R. Brook,et al.  The Koorin Expedition : atmospheric boundary layer data over tropical savannah land , 1979 .

[27]  Robert G. Lamb,et al.  A numerical simulation of dispersion from an elevated point source in the convective planetary boundary layer , 1978 .

[28]  John D. Reid.  Markov Chain Simulations of Vertical Dispersion in the Neutral Surface Layer for Surface and Elevated Releases , 1979 .

[29]  J. O'Brien,et al.  A Note on the Vertical Structure of the Eddy Exchange Coefficient in the Planetary Boundary Layer , 1970 .

[30]  L. Richardson,et al.  Atmospheric Diffusion Shown on a Distance-Neighbour Graph , 1926 .

[31]  S. Caughey,et al.  Some aspects of turbulence structure through the depth of the convective boundary layer , 1979 .

[32]  M. Raupach,et al.  Markov-chain simulation of particle dispersion in inhomogeneous flows: The mean drift velocity induced by a gradient in Eulerian velocity variance , 1982 .

[33]  R. Pielke,et al.  Diurnal Boundary-Layer Development over Sloping Terrain , 1981 .

[34]  S. Barr,et al.  The random force theory applied to regional scale tropospheric diffusion , 1987 .

[35]  D. Williams,et al.  The long-range dispersion of a plume from an isolated point source , 1981 .

[36]  E. F. Bradley,et al.  Flux-Profile Relationships in the Atmospheric Surface Layer , 1971 .