Dispersion of a Passive Tracer in Buoyancy- and Shear-Driven Boundary Layers

Alessandro Dosio Meteorology and Air Quality Section, Wageningen University, Wageningen, Netherlands

Search for other papers by Alessandro Dosio in
Current site
Google Scholar
PubMed
Close
,
Jordi Vilà-Guerau de Arellano Meteorology and Air Quality Section, Wageningen University, Wageningen, Netherlands

Search for other papers by Jordi Vilà-Guerau de Arellano in
Current site
Google Scholar
PubMed
Close
,
Albert A. M. Holtslag Meteorology and Air Quality Section, Wageningen University, Wageningen, Netherlands

Search for other papers by Albert A. M. Holtslag in
Current site
Google Scholar
PubMed
Close
, and
Peter J. H. Builtjes TNO-MEP, Apeldoorn, Netherlands

Search for other papers by Peter J. H. Builtjes in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

By means of finescale modeling [large-eddy simulation (LES)], the combined effect of thermal and mechanical forcing on the dispersion of a plume in a convective boundary layer is investigated. Dispersion of a passive tracer is studied in various atmospheric turbulent flows, from pure convective to almost neutral, classified according to the scaling parameters u∗/w∗ and −zi/L. The LES results for the flow statistics and dispersion characteristics are first validated for pure convective cases against the available results from laboratory and field experiments. Currently used parameterizations are evaluated with the model results. The effect of wind shear is studied by analyzing the dynamic variables, in particular the velocity variances, and their relation with the dispersion characteristics, specifically plume mean height, dispersion parameters, ground concentrations, and concentration fluctuations. The main effect of the wind shear results in a reduction of the vertical spread and an enhancement of the horizontal dispersion. This effect greatly influences the behavior of the ground concentrations because the tracer is transported by the wind for a longer time before reaching the ground. The vertical dispersion parameter is studied by discussing the two main components: meandering and relative diffusion. Results show that the increasing wind reduces the plume vertical motion. The influence of increasing wind shear on the concentration fluctuation intensity is also analyzed. The limited plume vertical looping in conditions of weak convection results in reduction of the concentration fluctuation intensity. Parameterizations for the dispersion parameters are derived as a function of the flow characteristics, namely, the shear–buoyancy ratio, velocity variances, and wind shear. The parameterizations are partially based on previous studies and are verified for the different buoyancy- and shear-driven flows, showing satisfactory agreement with the model results.

Corresponding author address: A. Dosio, Meteorology and Air Quality Section, Wageningen University, 6701 AP Wageningen, Netherlands. alessandro.dosio@wur.nl

Abstract

By means of finescale modeling [large-eddy simulation (LES)], the combined effect of thermal and mechanical forcing on the dispersion of a plume in a convective boundary layer is investigated. Dispersion of a passive tracer is studied in various atmospheric turbulent flows, from pure convective to almost neutral, classified according to the scaling parameters u∗/w∗ and −zi/L. The LES results for the flow statistics and dispersion characteristics are first validated for pure convective cases against the available results from laboratory and field experiments. Currently used parameterizations are evaluated with the model results. The effect of wind shear is studied by analyzing the dynamic variables, in particular the velocity variances, and their relation with the dispersion characteristics, specifically plume mean height, dispersion parameters, ground concentrations, and concentration fluctuations. The main effect of the wind shear results in a reduction of the vertical spread and an enhancement of the horizontal dispersion. This effect greatly influences the behavior of the ground concentrations because the tracer is transported by the wind for a longer time before reaching the ground. The vertical dispersion parameter is studied by discussing the two main components: meandering and relative diffusion. Results show that the increasing wind reduces the plume vertical motion. The influence of increasing wind shear on the concentration fluctuation intensity is also analyzed. The limited plume vertical looping in conditions of weak convection results in reduction of the concentration fluctuation intensity. Parameterizations for the dispersion parameters are derived as a function of the flow characteristics, namely, the shear–buoyancy ratio, velocity variances, and wind shear. The parameterizations are partially based on previous studies and are verified for the different buoyancy- and shear-driven flows, showing satisfactory agreement with the model results.

Corresponding author address: A. Dosio, Meteorology and Air Quality Section, Wageningen University, 6701 AP Wageningen, Netherlands. alessandro.dosio@wur.nl

Save
  • Briggs, G. A. 1985. Analytical parameterization of diffusion: The convective boundary layer. J. Climate Appl. Meteor. 24:11671186.

  • Briggs, G. A. 1993. Plume dispersion in the convective boundary layer. Part II: Analyses of CONDORS field experiment data. J. Appl. Meteor. 32:13881425.

    • Search Google Scholar
    • Export Citation
  • Caughey, S. J. and S. G. Palmer. 1979. Some aspects of turbulence structure through the depth of the convective boundary layer. Quart. J. Roy. Meteor. Soc. 105:811827.

    • Search Google Scholar
    • Export Citation
  • Cuijpers, J. W. M. and P. G. Duynkerke. 1993. Large eddy simulation of trade wind cumulus clouds. J. Atmos. Sci. 50:38943908.

  • Deardorff, J. W. and G. E. Willis. 1984. Ground level concentration fluctuations from a buoyant and non-buoyant source within a laboratory convectively mixed layer. Atmos. Environ. 18:12971309.

    • Search Google Scholar
    • Export Citation
  • Deardorff, J. W. and G. E. Willis. 1985. Further results from a laboratory model of the convective planetary boundary layer. Bound-Layer Meteor. 32:205236.

    • Search Google Scholar
    • Export Citation
  • Fackrell, J. E. and A. G. Robins. 1982. Concentration fluctuations and fluxes in plumes from point sources in a turbulent boundary layer. J. Fluid Mech. 117:126.

    • Search Google Scholar
    • Export Citation
  • Fedorovich, E. and J. Thäter. 2002. A wind tunnel study of gaseous tracer dispersion in the convective boundary layer capped by a temperature inversion. Atmos. Environ. 36:22452255.

    • Search Google Scholar
    • Export Citation
  • Fedorovich, E., F. T. M. Nieuwstadt, and R. Kaiser. 2001. Numerical and laboratory study of horizontally evolving convective boundary layer. Part II: Effects of elevated wind shear and surface roughness. J. Atmos. Sci. 58:546560.

    • Search Google Scholar
    • Export Citation
  • Gopalakrishnan, S. G. and R. Avissar. 2000. An LES study of the impacts of land surface heterogeneity on dispersion in the convective boundary layer. J. Atmos. Sci. 57:352371.

    • Search Google Scholar
    • Export Citation
  • Gryning, S. E., A. A. M. Holtslag, J. S. Irwin, and B. Siversten. 1987. Applied dispersion modelling based on meteorological scaling parameters. Atmos. Environ. 21:7989.

    • Search Google Scholar
    • Export Citation
  • Henn, D. S. and R. I. Sykes. 1992. Large eddy simulation of dispersion in the convective boundary layer. Atmos. Environ. 26A:31453159.

    • Search Google Scholar
    • Export Citation
  • Holtslag, A. A. M. and F. T. M. Nieuwstadt. 1986. Scaling the atmospheric boundary layer. Bound.-Layer Meteor. 36:201209.

  • Lamb, R. G. 1978. A numerical simulation of dispersion from an elevated point source in the convective planetary boundary layer. Atmos. Environ. 12:12971304.

    • Search Google Scholar
    • Export Citation
  • Lamb, R. G. 1982. Diffusion in the convective boundary layer. Atmospheric Turbulence and Air Pollution Modelling, F. T. M. Nieuwstadt and H. van Dop, Eds., Reidel, 159–229.

    • Search Google Scholar
    • Export Citation
  • Lenschow, D. H., J. C. Wyngaad, and W. T. Pennell. 1980. Mean-field and second-moment budgets in a baroclinic, convective boundary layer. J. Atmos. Sci. 37:13131326.

    • Search Google Scholar
    • Export Citation
  • Liu, C. H. and D. Y. C. Leung. 2001. Turbulence and dispersion studies using a three-dimensional second-order closure Eulerian Model. J. Appl. Meteor. 40:92113.

    • Search Google Scholar
    • Export Citation
  • Luhar, A. K. 2002. The influence of vertical wind direction shear on dispersion in the convective boundary layer and its incorporation in coastal fumigation models. Bound.-Layer Meteor. 102:138.

    • Search Google Scholar
    • Export Citation
  • Mason, P. J. 1992. Large-eddy simulation of dispersion in convective boundary layers with wind shear. Atmos. Environ. 26A:15611571.

  • Moeng, C-H. and P. P. Sullivan. 1994. A comparison of shear- and buoyancy-driven planetary boundary layer flows. J. Atmos. Sci. 51:9991022.

    • Search Google Scholar
    • Export Citation
  • Nieuwstadt, F. T. M. 1980. Application of mixed-layer similarity to the observed dispersion from a ground-level source. J. Appl. Meteor. 19:157162.

    • Search Google Scholar
    • Export Citation
  • Nieuwstadt, F. T. M. 1992. A large-eddy simulation of a line source in a convective atmospheric boundary layer—I. Dispersion characteristics. Atmos. Environ. 26A:485495.

    • Search Google Scholar
    • Export Citation
  • Nieuwstadt, F. T. M. and J. P. J. M. M. de Valk. 1987. A large eddy simulation of buoyant and non-buoyant plume dispersion in the atmospheric boundary layer. Atmos. Environ. 21:25732587.

    • Search Google Scholar
    • Export Citation
  • Nieuwstadt, F. T. M., P. J. Mason, C. H. Moeng, and U. Schumann. 1991. Large-eddy simulation of the convective boundary layer: A comparison of four computer codes. Proceedings of the Eighth Symposium on Turbulent Shear Flows, F. Durst, Ed., Springer-Verlag, 343–367.

    • Search Google Scholar
    • Export Citation
  • Schmidt, H. and U. Schumann. 1989. Coherent structure of the convective boundary layer derived from large-eddy simulations. J. Fluid Mech. 200:511562.

    • Search Google Scholar
    • Export Citation
  • Siebesma, A. P. and J. W. M. Cuijpers. 1995. Evaluation of parametric assumptions for shallow cumulus convection. J. Atmos. Sci. 52:650666.

    • Search Google Scholar
    • Export Citation
  • Sykes, R. I. and D. S. Henn. 1989. Large-eddy simulation of turbulent sheared convection. J. Atmos. Sci. 46:11061119.

  • Sykes, R. I. and D. S. Henn. 1992. Large eddy simulation of concentration fluctuations in a dispersing plume. Atmos. Environ. 26A:31273144.

    • Search Google Scholar
    • Export Citation
  • van Haren, L. and F. T. M. Nieuwstadt. 1989. The behavior of passive and buoyant plumes in a convective boundary layer, as simulated with a large-eddy model. J. Appl. Meteor. 28:818832.

    • Search Google Scholar
    • Export Citation
  • Venkatram, A. 1988. Dispersion in the stable boundary layer. Lectures on Air Pollution Modeling, A. Venkatram and J. C. Wyngaard, Eds., Amer. Meteor. Soc., 228–265.

    • Search Google Scholar
    • Export Citation
  • Vreugdenhil, C. B. and B. Koren. Eds.,. 1993. Numerical Methods for Advection–Diffusion Problems. Vol. 45, Notes on Numerical Fluid Mechanics, Vieweg, 373 pp.

    • Search Google Scholar
    • Export Citation
  • Weil, J. C. 1988. Dispersion in the convective boundary layer. Lectures on Air Pollution Modeling, A. Venkatram and J. C. Wyngaard, Eds., Amer. Meteor. Soc., 167–227.

    • Search Google Scholar
    • Export Citation
  • Weil, J. C., W. Synder, R. E. Lawson Jr., and M. S. Shipman. 2002. Experiments on buoyant plume dispersion in a laboratory convection tank. Bound.-Layer Meteor. 102:367414.

    • Search Google Scholar
    • Export Citation
  • Willis, G. E. and J. W. Deardorff. 1974. A laboratory model for the unstable boundary layer. J. Atmos. Sci. 31:12971307.

  • Willis, G. E. and J. W. Deardorff. 1976. A laboratory model of diffusion into the convective planetary boundary layer. Quart. J. Roy. Meteor. Soc. 102:427445.

    • Search Google Scholar
    • Export Citation
  • Willis, G. E. and J. W. Deardorff. 1981. A laboratory study of dispersion from a source in the middle of the convectively mixed layer. Atmos. Environ. 15:109117.

    • Search Google Scholar
    • Export Citation
  • Zeman, O. and H. Tennekes. 1977. Parameterization of the turbulent energy budget at the top of the daytime atmospheric boundary layer. J. Atmos. Sci. 34:111123.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 482 167 3
PDF Downloads 135 37 0