Abstract
A 1D Canopy Interface Model (CIM) is developed to act as an interface between a meso-scale and a micro-scale atmospheric model and to better resolve the surface turbulent fluxes in the urban canopy layer. A new discretisation is proposed to solve the TKE equation finding solutions that remain fully concordant with the surface layer theories developed for neutral flows over flat surfaces. A correction is added in the buoyancy term of the TKE equation to improve consistency with the Monin-Obukhov surface layer theory. Obstacles of varying heights and dimensions are taken into account by introducing specific terms in the equations and by modifying the mixing length formulation in the canopy layer. The results produced by CIM are then compared with wind and TKE profiles simulated with a LES experiment and results obtained during the BUBBLE meteorological intensive observation campaign. It is shown that the CIM computations are in good agreement with the results simulated by the LES as well as the measurements from BUBBLE. The applicability of the correction term in an urban canopy layer and to further validate CIM in multiple stability conditions and various urban configurations is discussed.
Highlights
Boundary layer laws have been developed since a very long time
We propose a correction for the production term of the turbulent kinetic energy (TKE) equation to improve the concordance between the results simulated using the simplified One dimension (1D) Navier-Stokes equations and the results calculated with the Monin-Obukhov laws
Verification of the New Discretization Scheme To verify the new discretization scheme adopted in Canopy Interface Model (CIM), we compare the results obtained in a neutral case with the analytical solution from the surface layer theory
Summary
Boundary layer laws have been developed since a very long time. Important characteristics of the surface layer were first described by Prandtl (1925) and these were recognized as the Prandtl or constant flux layer theories. Several studies were conducted to improve the mathematical representation of the different processes taking place in this surface layer and under different atmospheric stability conditions (Monin and Obukhov, 1954; Foken, 2006; Zilitinkevich and Esau, 2007) These theories have been extensively validated with measurements from wind tunnels (Cermak, 1971) as well as measurements in real situations (Businger et al, 1971; Högström, 1990; Beljaars and Holtslag, 1991; Oncley et al, 1996).
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