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Leipzig Stratified

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Scope

The benchmark is open to participants of the Wakebench project using atmospheric boundary layer models that include thermal stratification.

Objectives

Parameterize the ABL to obtain the best fit to the Leipzig profile and report on the resulting boundary layer characteristics.

Data Accessibility

The benchmark is offered to participants of the IEA Task 31 Wakebench. In the future it will be open for public access.

Input data

The conditions for simulating the Leipzig wind profile in stable conditions are:

  • Inlet profiles of velocity components and turbulent viscosity
  • Coriolis parameter: fc =1.3e-4 s-1
  • Use dry air with a density ρ = 1.225 kg/m3 and dynamic viscosity μ = 1.73e-5 kg/ms

Validation data

The validation profiles are the same as the inlet profiles, as obtained from Lettau (1950). The participant is asked to provide the best fit of the ABL model to these input data profiles.

Model runs

A 3 km high domain should be used, sufficient to fit the boundary layer height with some margin.

Output data

Please provide vertical profiles of velocity components (U,V), potential temperature (Θ), turbulent kinetic energy (tke) and turbulent viscosity (νt), using the file naming and format convention described in the Windbench user's guide with profID = outlet. Hence, the output profile file contains the following variables (header), in this order: Z(m), U(m/s), V(m/s), T(K), tke(m2/s2), nu_t(m2/s).
Please also report the following parameters:

  • in the surface-layer: Obukhov length (L), roughness length (z0), friction velocity (u*) and kinematic heat flux (wΘ)
  • in the upper layer: geostrophic wind (Ug), capping inversion strength (K/m) and boundary layer height (htke), defined as the height were the tke falls to 5% of the surface value

Remarks

Please report on the fitting methodology employed and the final settings of the model.