# Amauri Pereira de Oliveira Group of Micrometeorology Summer School Rio de Janeiro March 2009 2. PBL PROPERTIES.

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Amauri Pereira de Oliveira Group of Micrometeorology Summer School Rio de Janeiro March 2009 2. PBL PROPERTIES

2 Topics 1.Micrometeorology 2.PBL properties 3.PBL modeling 4.Modeling surface-biosphere interaction 5.Modeling Maritime PBL 6.Modeling Convective PBL

3 PBL PROPERTIES

4 Turbulent Boundary Layer (TBL) Monin. A.S. and Yaglom, A.M., 1971: Statistical Fluid Mechanics, Vol. 1, Massachussets: MIT Press, 769 pp. Rigid Surface Fluid is moving with velocity U U TBL

5 Turbulent Boundary Layer Monin and Yaglom, 1971. Scales characteristics: δ = vertical extension CLT; ν/u * = length scale; ν = kinematics viscosity of fluid (ν ar 1.5 m 2 /s); u * = velocity scale; h i = characteristic length scale for the roughness elements of the surface.

6 Internal and external TBL Raupach, M.R., Antonia, R.A. and Rajagopalan, S., 1991: Rough-wall turbulent boundary layers, Applied Mechanics Reviews, 44, 1-25. The TBL can be divided to layers using as a criteria the source of turbulence Internal layer (“inner-region”): Shear is intense and most of the turbulence is produced; Characteristic length scale is ν/u * ; External layer (“outer-region”): Shear is small and production of turbulence is also small; Characteristic length scale is δ.

7 Rough and smooth surfaces A surface is aerodynamically smooth when the vertical extension of roughness elements (h i ) are smaller than ν/u *. In this case there is a layer adjacent to the surface where the vertical profile of mean velocity varies linearly with height. It is frequently called viscous sub layer. The region of turbulence production is located in the viscous sub layer (internal or inner layer).

8 Canonical TBL – Smooth surface Surface rigid and plane; Horizontal pressure gradient null; No thermal stratification (Neutral flow) Aerodynamically smooth surface Stationary flow

9 Canonic TBL Monin. and Yaglom (1971). Linear profile Logarithmic profile

10 TBL – Rough surfaces Raupach et al., 1991.

11 Planetary Boundary Layer Planetary Boundary Layer (PBL) is the region - adjacent to the surface - where turbulence promotes mixing and most of the exchange of energy, mass and momentum between the surface and atmosphere.

12 PBL localization Turbulent layer

13 Diurnal evolution Adapted from Stull (1988 ).

14 Homogeneous and plane surfaces Jatos de baixos níveis Sem memória Fernando, H.J.S., Lee, S.M., Anderson, J., Princevac, M., Pardyjak, E. and Grossman-Clarke, S., 2001: Urban fluid mechanics: air circulation and contaminant dispersion in cities. Environmental Fluid Mechanics, 1, 107-164.

15 Convective PBL Nieuwstadt, F.T.M. and Duynkerke, P.G., 1996: Turbulence in the boundary layer, Atmospheric Research, 40, 111-142.

16 Similarity Theory - CBL Monin and Obukhov similarity Nieuwstadt and Duynkerke, 1996. Mixing Layer Similarity Free Convection Similarity

17 Monin-Obukhov Similarity Nieuwstadt and Duynkerke, 1996. Characteristic length scale Obukhov length scale

18 Mixing Layer Similarity Nieuwstadt and Duynkerke, 1996.

19 Stable Boundary Layer - SBL Nieuwstadt and Duynkerke, 1996.

20 Nieuwstadt and Duynkerke, 1996. Similarity theory for SBL

21 Local Similarity Local Obukhov length scale. Characteristic length scale Nieuwstadt and Duynkerke, 1996.

22 Vertical structure of SBL Nieuwstadt and Duynkerke, 1996.

23 PBL over heterogeneous surface Urban Boundary Layer Source: Fernando et al. (2001).

24 BPL – Complex Topography Source: Hunt et al., 2003 Advection makes turbulence not local.

25 Surface covered by vegetation Mahrt, L., 2000: Surface heterogeneity and vertical structure of the boundary layer. Boundary-Layer Meteorology, 96: 33-62. Internal layer: Inertial layer; Roughness layer; Canopy layer; Canopy sub-layer.

26 Canopy layer turbulent fluxes Finnigan, J., 2000: Turbulence in plant canopies. Annu. Rev. Fluid Mech., 32, 519–571.

27 PBL over the ocean. Sjöblom, A. and Smedam, A.-S., 2003: Vertical structure in the marine atmospheric boundary layer and its implication for the inertial dissipation method, Boundary-Layer Meteorology, 109, 1-25 Inertial layer; Roughness layer.

28 Urban Boundary Layer Internal region: Inertial; Roughness layer; Canopy layer; Canopy sub-layer. Fonte: Fernando et al. (2001).

29 UBL structure Fernando et al., 2001.

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