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Increasing urbanization motivates the studies of urban boundary processes, and mesoscale models with urban canopy parameterizations, such as the Weather Research and Forecast model, have been widely used. However, the simplified urban canopy model without considering detailed urban forms could lead to large uncertainties in predicting mesoscale weather and climate in cities. Using obstacle-resolving large-eddy simulations, we investigate the impact of variable vertical extent of the profiles of urban form in streamwise direction on the atmospheric boundary layer (ABL). Three types of idealized urban forms with the same mean building height but different streamwise inhomogeneity are designed and conducted under neutral condition. The non-local effects of different urban forms on the ABL are characterized by demarcating the ‘zones of urban influence’ in the upwind, downwind and vertical regions using objective metrics of the velocity field. This work highlights the importance of capturing urban forms, especially the height variation of buildings, in the current mesoscale-modelling framework. Further analysis of the difference in the transportation of heat and momentum among cases will be investigated in the future.

Keywords: Urban form; urban heat island; mesoscale modelling; large-eddy simulations.

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