• Deardorff, J. W., 1980: Stratocumulus-capped mixed layers derived from a three-dimensional model. Bound.-Layer Meteor., 18 , 495527.

  • Denby, B., 1999: Second-order modeling of turbulence in katabatic flows. Bound.-Layer Meteor., 92 , 67100.

  • Ducros, F., P. Comte, and M. Lesieur, 1996: Large-eddy simulation of transition to turbulence in a boundary layer developing spatially over a flat plate. J. Fluid Mech., 326 , 137.

    • Search Google Scholar
    • Export Citation
  • Horst, T. W., and J. C. Doran, 1986: Nocturnal drainage flow on simple slopes. Bound.-Layer Meteor., 34 , 263286.

  • Mahrt, L., 1982: Momentum balance of gravity flows. J. Atmos. Sci., 39 , 27012711.

  • Manins, P. C., and B. L. Sawford, 1979: A model of katabatic winds. J. Atmos. Sci., 36 , 619630.

  • Monti, P., H. J. S. Fernando, M. Princevac, W. C. Chan, T. A. Kowalewski, and E. R. Pardyjak, 2002: Observations of flow and turbulence in the nocturnal boundary layer over a slope. J. Atmos. Sci., 59 , 25132534.

    • Search Google Scholar
    • Export Citation
  • Nappo, C. J., and S. Rao, 1987: A model study of pure katabtic flows. Tellus, 39A , 6171.

  • Oerlemans, J., 1998: The atmospheric boundary layer over melting glaciers. Clear and Cloudy Boundary Layers, A. A. M. Holtslag and P. G. Duynkerke, Eds., Royal Netherlands Academy of Arts and Sciences, 129–153.

    • Search Google Scholar
    • Export Citation
  • Oerlemans, J., and B. Grisogono, 2002: Glacier winds and parameterisation of the related surface heat fluxes. Tellus, 54A , 440462.

  • Prandtl, L., 1942: Führer Durch die Strömunglehre. Braunschweig, F. Vieweg & sohn, 382 pp. [Published in English in 1952 as Essentials of Fluid Dynamics, Hafner, 452 pp.].

    • Search Google Scholar
    • Export Citation
  • Renfrew, I. A., and P. S. Anderson, 2002: The surface climatology of an ordinary katabatic wind regime in Coats Land, Antarctica. Tellus, 54A , 463484.

    • Search Google Scholar
    • Export Citation
  • Skyllingstad, E. D., 2003: Large eddy simulation of katabatic flows. Bound.-Layer Meteor., 106 , 217243.

  • Smeets, P., P. Duynkerke, and H. Vugts, 1998: Turbulence characteristics of the stable boundary layer over a mid-latitude glacier. Part I: A combination of katabatic and large scale forcing. Bound.-Layer Meteor., 87 , 117145.

    • Search Google Scholar
    • Export Citation
  • Steppler, J., H-W. Bitzer, M. Minotte, and L. Bonaventura, 2002: Nonhydrostatic atmospheric modeling using a z-coordinate representation. Mon. Wea. Rev., 130 , 21432149.

    • Search Google Scholar
    • Export Citation
  • Xue, M., K. Droegemeier, and V. Wong, 2000: The Advanced Regional Prediction System (ARPS)—A multi-scale nonhydrostatic atmospheric simulation and prediction model. Part I: Model dynamics and verification. Meteor. Atmos. Phys., 75 , 161193.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 143 69 2
PDF Downloads 98 41 0

Numerical Simulation of Katabatic Flow with Changing Slope Angle

View More View Less
  • 1 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
Restricted access

Abstract

A large eddy simulation (LES) model and the Advanced Regional Prediction System (ARPS) model, which does not resolve turbulent eddies, are used to study the effect of a slope angle decrease on the structure of katabatic slope flows. For a simple, uniform angle slope, simulations from both models produce turbulence kinetic energy and momentum budgets that are in good overall agreement. Simulations of a compound angle slope are compared to a uniform angle slope to demonstrate how a changing slope angle can strongly affect the strength of katabatic flows. Both ARPS and the LES model show that slopes with a steep upper slope followed by a shallower lower slope (concave shape) generate a rapid acceleration on the upper slope followed by a transition to a slower evolving structure characterized by an elevated jet over the lower slope. In contrast, the case with uniform slope (having the same total height change) yields a more uniform flow profile with stronger winds at the slope bottom. Higher average slope in the uniform slope angle case generates greater gravitational potential energy, which is converted to kinetic energy at the bottom of the slope. Analysis of the total energy budget of slope flows indicates a consistent structure where potential energy generated at the top of the slope is transported downslope and converted into kinetic energy near the slope base.

Corresponding author address: Craig Smith, COAS, 104 COAS Admin. Bldg., Oregon State University, Corvallis, OR 97331. Email: csmith@coas.oregonstate.edu

Abstract

A large eddy simulation (LES) model and the Advanced Regional Prediction System (ARPS) model, which does not resolve turbulent eddies, are used to study the effect of a slope angle decrease on the structure of katabatic slope flows. For a simple, uniform angle slope, simulations from both models produce turbulence kinetic energy and momentum budgets that are in good overall agreement. Simulations of a compound angle slope are compared to a uniform angle slope to demonstrate how a changing slope angle can strongly affect the strength of katabatic flows. Both ARPS and the LES model show that slopes with a steep upper slope followed by a shallower lower slope (concave shape) generate a rapid acceleration on the upper slope followed by a transition to a slower evolving structure characterized by an elevated jet over the lower slope. In contrast, the case with uniform slope (having the same total height change) yields a more uniform flow profile with stronger winds at the slope bottom. Higher average slope in the uniform slope angle case generates greater gravitational potential energy, which is converted to kinetic energy at the bottom of the slope. Analysis of the total energy budget of slope flows indicates a consistent structure where potential energy generated at the top of the slope is transported downslope and converted into kinetic energy near the slope base.

Corresponding author address: Craig Smith, COAS, 104 COAS Admin. Bldg., Oregon State University, Corvallis, OR 97331. Email: csmith@coas.oregonstate.edu

Save