Amauri Pereira de OliveiraGroup of Micrometeorology Summer SchoolRio de JaneiroMarch 2009

2. PBL PROPERTIES

TopicsMicrometeorology PBL propertiesPBL modelingModeling surface-biosphere interactionModeling Maritime PBLModeling Convective PBL

PBL PROPERTIES

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

Turbulent Boundary LayerMonin and Yaglom, 1971.Scales characteristics:

= vertical extension CLT;

/u* = length scale;

= kinematics viscosity of fluid (ar 1.5 m2/s);

u* = velocity scale;

hi = characteristic length scale for the roughness elements of the surface.

Internal and external TBLRaupach, 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 /u* ;

External layer (outer-region):Shear is small and production of turbulence is also small;Characteristic length scale is .

Rough and smooth surfaces A surface is aerodynamically smooth when the vertical extension of roughness elements (hi) are smaller than /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).

Canonical TBL Smooth surfaceSurface rigid and plane;Horizontal pressure gradient null;No thermal stratification (Neutral flow)Aerodynamically smooth surfaceStationary flow

Canonic TBLMonin. and Yaglom (1971).Linear profileLogarithmic profile

TBL Rough surfacesRaupach et al., 1991.

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.

PBL localization Turbulent layer

Diurnal evolutionAdapted from Stull (1988).

Homogeneous and plane surfacesJatos de baixos nveisSem memriaFernando, 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.

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

Similarity Theory - CBLMonin and Obukhov similarityNieuwstadt and Duynkerke, 1996.Mixing Layer SimilarityFree Convection Similarity

Monin-Obukhov SimilarityNieuwstadt and Duynkerke, 1996.Characteristic length scaleObukhov length scale

Mixing Layer SimilarityNieuwstadt and Duynkerke, 1996.

Stable Boundary Layer - SBLNieuwstadt and Duynkerke, 1996.

Nieuwstadt and Duynkerke, 1996.Similarity theory for SBL

Local SimilarityLocal Obukhov length scale.Characteristic length scaleNieuwstadt and Duynkerke, 1996.

Vertical structure of SBLNieuwstadt and Duynkerke, 1996.

PBL over heterogeneous surfaceUrban Boundary LayerSource: Fernando et al. (2001).

BPL Complex TopographySource: Hunt et al., 2003 Advection makes turbulence not local.

Surface covered by vegetationMahrt, 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.

Canopy layer turbulent fluxesFinnigan, J., 2000: Turbulence in plant canopies. Annu. Rev. Fluid Mech., 32, 519571.

PBL over the ocean.

Sjblom, 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, 1-25Inertial layer;Roughness layer.

Urban Boundary LayerInternal region:Inertial;Roughness layer;Canopy layer;Canopy sub-layer.

Fonte: Fernando et al. (2001).

UBL structureFernando et al., 2001.