Merging the Gap Between Meso and Micro Scales: Enhanced Inflow Boundary Conditions for CFD Modeling of Urban Air Quality

Abstract

Despite the advent of high performance numerical tools, the spatial gap between meso and microscale models is still a challenge in atmospheric modeling. The way boundary conditions are prescribed is crucial for the correct linkage between scales, especially in inhomogeneous canopies, which induce complex airflow dynamics and pollutant concentration patterns. The purpose of this work is to evaluate the sensitivity of microscale modeling results to distinct methods of deriving inflow vertical wind profiles in urban areas. The methodology involves the comparison of three methods for prescribing inflow profiles: (1) Log wind profile based on meteorological observations, (2) the mesoscale model WRF running at 200 m resolution, and (3) the LES model ARPS. The different profiles obtained were fed into the CFD model VADIS. The comparison of results against measured SF6 concentrations shows that ARPS is capable of accounting for upwind region characteristics, providing more reliable inflow conditions. Moreover, VADIS has provided an enhanced and detailed insight over the 3D wind flow behaviour, accounting for the effects of buildings and trees, and its effect over dispersion. © Springer Science+Business Media Dordrecht 2014.