The Importance of Boundary Layer Wind Veer for Urban Transport and Dispersion of Contaminants: Implementation of a New 1D RANS Scheme into the QUIC Modeling System

Recent numerical research and field programs have underscored the significance of accurate inflow meteorological conditions for proper simulations of urban dispersion and transport of pollutants. Specifically, wind shear (i.e., wind speed vertical gradient) and veer (i.e., wind direction vertical gradient) in the atmospheric boundary layer have emerged as key parameters for accurate dispersion predictions. In this study, we introduce and implement an innovative approach for determining the inflow conditions in the Quick Urban & Industrial Complex (QUIC) diagnostic wind solver, with the goal of accounting for different physical processes producing wind veer and shear. The new inflow scheme is fast to compute, relies on a coupled system of Ordinary Differential Equations (ODEs) derived from the RANS equations and can model the effects of different physical mechanisms (e.g., surface roughness, turbulent stress, Coriolis force, buoyancy and baroclinicity) on the boundary layer vertical profiles and ultimately on wind veer and shear.

During the talk, I will introduce the basic formulation of the new scheme, show its verification against idealized and expensive 3D Large Eddy Simulations tests with the GPU-based FastEddy, and present results of an evaluation exercise with field data from a wind lidar and a release tracer experiment. By analyzing comparisons with established inflow capabilities of QUIC that do not take into account wind veer (Monin-Obukhov similarity theory), I will highlight QUIC sensitivity to wind veer and draw general conclusions on the importance of including wind veer in urban transport and dispersion calculations.