Spatial and temporal variability of turbulent fluxes in the Joint Urban 2003 street canyon

A flow characterization study was conducted to investigate the details of turbulent processes occurring in a real urban street canyon as part of the Joint Urban 2003 tracer dispersion field experiment held in downtown Oklahoma city during the month of July 2003. The turbulence inside the street canyon is highly localized and sensitive to upwind boundary conditions. This is due to inhomogeneities associated with urban complexities such as morphology and varying surface properties. This remains a major challenge for quantifying turbulence in a real urban canyon.

As part of this work, the spatial variation of shear stresses has been investigated and compared to an existing street canyon shear stress model. This model reproduces several of the salient characteristics of the actual shear stresses in an urban street canyon including, very low stresses deep in the canopy, maximum stresses at the roof top level and decreasing stresses in the remainder of the roughness sublayer. In this paper the above model is compared with actual data from the Oklahoma city street canyon. In particular the heat flux and shear stresses are quantified and compared to the model. Initial results suggests that the shear stress inside the street canyon is very low and almost zero, obeying with the model.