Wind-tunnel experiments of turbulent wake flows induced by steep topography in thermally-stratified boundary layers

Turbulent wakes downwind of complex topography with a steep slope are characterized by flow separation, reattachment and development of a new boundary layer. The turbulent fluxes of momentum and scalars in the wake, key to quantify the land-atmospheric interaction, are very challenging to predict even with the most advanced numerical models. This issue becomes more severe when the thermal stability of the atmospheric boundary layer (ABL) needs to be modelled. To address the coupled effects of steep-slope topography and thermal stability on turbulent transport near the ground, wind-tunnel measurements of velocity, temperature and heat flux were conducted using idealized steep topography models (including 2D and 3D blocks and hills) in thermally-stratified boundary layers. This presentation will focus on the analysis of the turbulent flow properties, the surface momentum and heat fluxes in different flow regimes, as well as how the surface fluxes are related to the fluid dynamics. Such knowledge is expected to facilitate the development of new parameterizations for surface fluxes and the validation of numerical models dealing with complex terrain.