Articles | Volume 16, issue 10
Atmos. Chem. Phys., 16, 6285–6301, 2016
https://doi.org/10.5194/acp-16-6285-2016
Atmos. Chem. Phys., 16, 6285–6301, 2016
https://doi.org/10.5194/acp-16-6285-2016

Research article 24 May 2016

Research article | 24 May 2016

Evaluating the impact of built environment characteristics on urban boundary layer dynamics using an advanced stochastic approach

Jiyun Song and Zhi-Hua Wang Jiyun Song and Zhi-Hua Wang
  • School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287, USA

Abstract. Urban land–atmosphere interactions can be captured by numerical modeling framework with coupled land surface and atmospheric processes, while the model performance depends largely on accurate input parameters. In this study, we use an advanced stochastic approach to quantify parameter uncertainty and model sensitivity of a coupled numerical framework for urban land–atmosphere interactions. It is found that the development of urban boundary layer is highly sensitive to surface characteristics of built terrains. Changes of both urban land use and geometry impose significant impact on the overlying urban boundary layer dynamics through modification on bottom boundary conditions, i.e., by altering surface energy partitioning and surface aerodynamic resistance, respectively. Hydrothermal properties of conventional and green roofs have different impacts on atmospheric dynamics due to different surface energy partitioning mechanisms. Urban geometry (represented by the canyon aspect ratio), however, has a significant nonlinear impact on boundary layer structure and temperature. Besides, managing rooftop roughness provides an alternative option to change the boundary layer thermal state through modification of the vertical turbulent transport. The sensitivity analysis deepens our insight into the fundamental physics of urban land–atmosphere interactions and provides useful guidance for urban planning under challenges of changing climate and continuous global urbanization.

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Short summary
In this study, we found that the apparent impact of landscape changes due to urbanization is far beyond a localized effect limited in a relatively shallow layer of atmosphere above a city. Instead, it can effectively penetrate into the deep layer of atmosphere above cities up to kilometres in height. Some of the landscape characteristics, e.g., the urban morphology, even exhibit peculiar (nonlinear) effect that challenges our intuitive thinking and invites further investigations.
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