Abstract
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.
Highlights
Land surface connects soil layers and the overlying atmosphere by transferring momentum, heat, and water through the interface
We apply subset simulation to analyze the sensitivity of the coupled single layer urban canopy model (SLUCM)–single column model (SCM) to different input parameters
Note that the initial soil water content for green roofs in the SLUCM is set as 90 % saturated for the subsequent 13.5 h of simulation after the beginning of convective boundary layer (CBL) development such that the evaporative power of green roofs is not constrained by soil water
Summary
Land surface connects soil layers and the overlying atmosphere by transferring momentum, heat, and water through the interface. Landscape characteristics are critical in determining surface heat and moisture fluxes, which in turn regulate the atmospheric boundary layer dynamics in, e.g., mesoscale atmospheric modeling (McCumber and Pielke, 1981). Statistical analyses on observational and numerical data sets have shown that land– atmosphere interaction is an importance source of uncertainty in climate predictability (Betts et al, 1996; Orlowsky and Seneviratne, 2010; Trier et al, 2011). The predictive skill and robustness of regional and global climate models can be significantly improved with a better representation of land–atmosphere interactions, especially the soil moisture/temperature/precipitation interactions (Chen and Avissar, 1994; Chen and Dudhia, 2001; Phillips and Klein, 2014; Seneviratne et al, 2010)
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