Parameterization of atmospheric stratification slide Parameterization of atmospheric stratification and issues in connection with canopy flow Sogachev Andrey Wind Energy Division, Risø National Laboratory for Sustainable Energy , DTU, Building 118, Box 49, DK-4000, Roskilde, Denmark, anso@risoe.dtu.dk

SCADIS (scalar distribution) model: overview Basic equations: momentum, heat, moisture, scalars (CO2, SO2, O3), turbulent kinetic energy (E) One-and-a-half-order turbulence closure based on equations of E and ε (dissipation rate) : ( E-l, E-ε.) E-ω closure based on ω (ε/E) equation Terrain-following coordinate system Horizontal and vertical resolutions (depending on a specific problem) (Sogachev et al., 2002, 2004; Sogachev and Panferov, 2006; Sogachev et al., 2008, Sogachev 2009)

l o w e r b o u n d a r y c o n d i t i o n s SCADIS model: domain q(t), T(t), C(t), V(t), U(t) Clouds ( t ) T soil ), q F CO2 V = 0 , U = 0 Q t), l o w e r b o u n d a r y c o n d i t i o n s 3 - 5 km 1 - 10 km Upper boundary conditions (Sogachev et al., 2002, 2004; Sogachev and Panferov, 2006; Sogachev et al., 2008, Sogachev 2009)

SCADIS model: physical processes in the model grid-cell F CO2 E R H G y f x ¶ , 10 - 100 m advection (Sogachev et al., 2002, 2004; Sogachev and Panferov, 2006; Sogachev et al., 2008, Sogachev 2009)

Turbulence model: governing equations slide Turbulence model: governing equations with with

Accounting for plant drag and buoyancy: the traditional way slide Accounting for plant drag and buoyancy: the traditional way ? ( Raupach and Shaw, 1982 ) ( Apsley and Castro, 1997) (Blackadar, 1962)

Modelling of Askervein flow Askervein Hill topographic map (brawn isolines) and dimensionless speed-up, ΔS estimated by SCADIS at z = 10 m above the ground (colored field). Figure 1 also shows the reference site (RS) (with ΔS = 0 ), the 210o wind direction in our simulations and the lines A, AA and B along which the measurements were made. Background of Figure 1 is taken from Castro et al., 2003.

Modelling of Askervein flow (b) Dimensionless speed-up, ΔS at z = 10 m above the ground along lines A (a) and AA (b). During measurements along line AA two different sets of instruments were used.

Uncertainties: buoyancy slide Uncertainties: buoyancy (Baumert and Peters, 2000)

Uncertainties: dissipation ( Ayotte et al., 1999 ) (Sogachev and Panferov., 2006)

Accounting for plant drag and buoyancy: the revised way slide Accounting for plant drag and buoyancy: the revised way (Seginer et al., 1976) ( Raupach and Shaw, 1982 ) ( Apsley and Castro, 1997) (Blackadar, 1962) (Sogachev and Panferov, 2006 ) (Sogachev 2009 )

Accounting for plant drag and buoyancy: the revised way slide Accounting for plant drag and buoyancy: the revised way

Treatment of the plant drag ►The Elora corn canopy (Wilson et al., 1982; Wilson, 1988) ▲The Pine forest canopy (Katul and Chang, 1999) ◄Furry hill wind-tunnel experiment (Finnigan and Brunet, 1995) (after Sogachev and Panferov, 2006)

Treatment of the plant drag The basic requirement of K-theory – that the length scale of the mixing process be substantially smaller than that of the inhomogeneity in the mean scalar or momentum gradient (Corrsin 1974) – is not violated for disturbed flow and for slow spatial variation of cdA (Finnigan and Belcher, 2004). SCADIS reproduces the experimental variation in length scales (Sogachev and Panferov, 2006)

Verification: low-roughness surface Wind speed ( m s-1 ) Fig. 1 (a) ABL wind evolution and (b) surface characteristics: u* and Monin-Obukhov length, L, during fair weather over low-roughness land derived by E-ω model. Converse Prandtl number (Businger et al. 1971, Sogachev et al. 2002)

Uncertainties: Turbulent Prandtl number, Pr versus Ri slide Uncertainties: Turbulent Prandtl number, Pr versus Ri

Verification: low-roughness surface Fig. 2 (a) Wind evolutions and (b) wind profiles for different hours in the atmospheric surface layer during fair weather over low-roughness land derived by E-ω and analytical models. (Paulson, 1970)

Verification: forested surface (Laakso et al., 2007)

Uncertainties: buoyancy inside canopy slide Uncertainties: buoyancy inside canopy

Uncertainties: buoyancy inside canopy slide Uncertainties: buoyancy inside canopy (Sogachev and Panferov, 2006 ) ?

Uncertainties: buoyancy inside canopy slide Uncertainties: buoyancy inside canopy

Uncertainties: buoyancy inside canopy slide Uncertainties: buoyancy inside canopy H =16 m, LAI = 1.38 (Christen and Novak, 2008)

slide ABL evolution

Energy budget above canopy layer slide Energy budget above canopy layer

slide Ri in ABL

slide Low-level jet

Low-level jet effects on wind energy related variables slide Low-level jet effects on wind energy related variables

slide Summary Much work remains to be done…