Article : Large-eddy simulation of katabatic winds. Part 2: Sensitivity study and comparison
Authors : Shapiro, A.School of Meteorology, University of Oklahoma, Norman, Oklahoma, USA, firstname.lastname@example.org, Axelsen, S. L.IMAU, Utrecht University, Utrecht, The Netherlands, email@example.com, Axelsen, S. L.IMAU, Utrecht University, Utrecht, The Netherlands, firstname.lastname@example.org,
Abstract : The effects of the slope angle, surface buoyancy flux, and background stratification on steady-state katabatic winds are studied using large-eddy simulation (LES). The numerical code was described and validated in a companion paper (Part 1). Our numerical results are interpreted in the light of analytical Prandtl model, and we find that our vertical profiles of the downslope velocity, buoyancy, and the momentum and buoyancy fluxes exhibit many of the features from the analytical solution. On the other hand, there are also differences between the analytical and numerical results due to the assumptions in the analytical model. One of the assumptions is that the Prandtl number is constant throughout the boundary layer. However, the simulations show that this number varies with height, and also that the Prandtl number increases with increasing gradient Richardson number. The immediate benefit of LES over analytical models is its capability of resolving turbulent motions. In our study of the turbulence kinetic energy budgets, we find that the wind shear is the largest production term, and that it is mainly balanced by turbulence dissipation. Near the wind maximum, where the shear vanishes, the turbulence transport is the only production term.
Bibliography : Axelsen, S.L., and H. van Dop (2009), Large-eddy simulation of katabatic winds. Part 1: Comparison with observations, Acta Geophys. 57, 4, 803-836.
Bange, J., and R. Roth (1999), Helicopter-borne flux measurements in the nocturnal boundary layer over land − a case study, Bound.-Layer Meteor. 92, 2, 295-325.
Basu, S., and F. Porté-Agel (2006), Large-eddy simulation of stably stratified atomspheric boundary layer turbulence: A scale-dependent dynamic modeling approach, J. Atmos. Sci. 63, 8, 2074-2091.
Beare, R.J., M.K. Macvean, A.A.M. Holtslag, J. Cuxart, I. Esau, J.-C. Golaz, M.A. Jimenez, M. Khairoutdinov, B. Kosovic, D. Lewellen, T.S. Lund, J.K. Lundquist, A. Mccabe, A.F. Moene, Y. Noh, S. Raasch, and P. Sullivan (2006), An intercomparison of large-eddy simulations of the stable boundary layer, Bound.-Layer Meteor. 118, 2, 247-272.
Cuxart, J., and M.A. Jiménez (2007), Mixing processes in a nocturnal low-level jet: an LES study, J. Atmos. Sci. 64, 5, 1666-1679.
Denby, B. (1999), Second-order modelling of turbulence in katabatic flows, Bound.-Layer Meteor. 92, 1, 65-98.
Fedorovich, E., and A. Shapiro (2009), Structure of numerically simulated katabatic and anabatic flows along steep slopes, Acta Geophys. 57, 4, 981-1010.
Grisogono, B. (2003), Post-onset behaviour of the pure katabatic flow, Bound.-Layer Meteor. 107, 1, 157-175.
Grisogono, B., and J. Oerlemans (2001a), Katabatic flow: Analytic solution for gradually varying eddy diffusivities, J. Atmos. Sci. 58, 21, 3349-3354.
Grisogono, B., and J. Oerlemans (2001b), A theory for the estimation of surface fluxes in simple katabatic flows, Quart. J. Roy. Met. Soc. 127, 578, 2725-2739.
Gutman, L.N., and V.M. Malbakhov (1964), On the theory of katabatic winds of Antarctica, Met. Issled. 9, 150-155 (in Russian).
Haiden, T., and C.D. Whiteman, (2005), Katabatic flow mechanisms on a low-angle slope, J. Appl. Meteorol. 44, 1, 113-126.
Kavčič, I., and B. Grisogono (2007), Katabatic flow with Coriolis effect and gradualny varying eddy diffusivity, Bound.-Layer Meteor. 125, 2, 377-387.
Klein, T., G. Heinemann, D.H. Bromwich, J.J. Cassano, and K.M. Hines (2001), Mesoscale modeling of katabatic winds over Greenland and comparisons with AWS and aircraft data, Meteorol. Atmos. Phys. 78, 1-2, 115-132.
Mahrt, L., and S. Larsen (1990), Relation of slope winds to the ambient flow over gentle terrain, Bound.-Layer Meteor. 53, 1-2, 93-102.
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, 17, 2513-2534.
Nappo, C.J., and K. Rao (1987), A model study of pure katabatic flows, Tellus 39A, 61-71.
Oerlemans, J. (1994), Quantifying global warming from the retreat of glaciers, Science 264, 5156, 243-245.
Oerlemans, J. (1998), The atmospheric boundary layer over melting glaciers. In: A.A.M. Holtslag, P.G. Duynkerke, and P.J. Jonker (eds.), Clear and Cloudy Boundary Layers, Royal Netherlands Academy of Arts and Sciences, Ch. 6, 129-153.
Oerlemans, J., H. Björnsson, M. Kuhn, F. Obleitner, F. Palsson, C.J.J.P. Smeets, H.F. Vugts, and J. De Wolde (1999), Glacio-meteorological investigations on Vatnajökull, Iceland, summer 1996: An overview, Bound.-Layer Meteor. 92, 1, 3-24.
Ohya, Y. (2001), Wind-tunnel study of atmospheric stable boundary layers over a rough surface, Bound.-Layer Meteor. 98, 1, 57-82.
Papadopoulos, K.H., C.G. Helmis, A.T. Soilemes, J. Kalogiros, P.G. Papageorgas, and D.N. Asimakopoulos (1997), The structure of katabatic flows down a simple slope, Quart. J. Roy. Met. Soc. 123, 542, 1581-1601.
Parmhed, O., J. Oerlemans, and B. Grisogono (2004), Describing surface fluxes in katabatic flow on Breidamerkurjökull, Iceland, Quart. J. Roy. Met. Soc. 130, 598, 1137-1151.
Prandtl, L. (1942), Führer durch die Strömungslehre, Vieweg und Sohn, Braunschweig.
Rao, K.S., and H.F. Snodgrass, (1981), A nonstationary nocturnal drainage flow model, Bound.-Layer Meteor. 20, 3, 309-320.
Sagaut, P. (1998), Large Eddy Simulation for Incompressible Flows: An Introduction, Springer-Verlag, Berlin, 319 pp.
Schumann, U. (1990), Large-eddy simulation of the up-slope boundary layer, Quart. J. Roy. Met. Soc. 116, 493, 637-670.
Shapiro, A., and E. Fedorovich (2008), Coriolis effects in homogeneous and inhomogeneous katabatic flows, Quart. J. Roy. Met. Soc. 134, 631, 353-370.
Skyllingstad, E.D. (2003), Large-eddy simulation of katabatic flows, Bound.-Layer Meteor. 106, 2, 217-243.
Stiperski, I., I. Kavčič, B. Grisogono, and D.R. Durran (2007), Including Coriolis effects in the Prandtl model for katabatic flow, Quart. J. Roy. Met. Soc. 133, 622, 101-106.
Strang, E.J., and H.J.S. Fernando (2001), Vertical mixing and transports through a stratified shear layer, J. Phys. Oceanography 31, 8, 2026-2048.
Stull, R.B. (1988), An Introduction to Boundary-Layer Meteorology, Kluwer Academic Publishers, 666 pp.
Van den Broeke, M.R. (1996), Characteristics of the lower ablation zone of the West Greenland ice sheet for energy-balance modelling, Ann. Glaciol. 23, 160-166.
Van den Broeke, M.R., N.P.M. van Lipzig, and E. van Meijgaard (2002), Momentum budget of the East-Antarctic atmospheric boundary layer: Results of a regional climate model, J. Atmos. Sci. 59, 3117-3129.
Whiteman, C.D. (1990), Observations of thermally developed wind systems in mountainous terrain. In: W. Blumen (ed.), Atmospheric Processes over Complex Terrain: Meteorological Monographs 23, 45, Am. Meteor. Soc., Boston, MA, Ch. 2, 5-42.
Whiteman, C.D., and S. Zhong (2008), Downslope flows on a low-angle slope and their interactions with valley inversions. Part I: Observations, J. Appl. Meteorol. Clim. 47, 7, 2023-2038, DOI: 10.1175/2007JAMC1669.1.
Zilitinkevich, S.S., T. Elperin, N. Kleeorin, I. Rogachevskii, I.N. Esau, T. Mauritsen, and M.W. Miles (2008), Turbulence energetics in stably stratified geophysical flows: Strong and weak mixing regimes, Quart. J. Roy. Met. Soc. 134, 633, 793-799.
Qute : Shapiro, A. ,Axelsen, S. L. ,Axelsen, S. L. ,Axelsen, S. L. , Large-eddy simulation of katabatic winds. Part 2: Sensitivity study and comparison. Acta Geophysica Vol. 57, no. 4/2009