title: Numerical study of the effects of Planetary Boundary Layer structure on the pollutant dispersion within built-up areas.
abstract: The effects of different Planetary Boundary Layer (PBL) structures on pollutant dispersion processes within two idealized street canyon configurations and a realistic urban area were numerically examined by a Computational Fluid Dynamics (CFD) model. The boundary conditions of different PBL structures/conditions were provided by simulations of the Weather Researching and Forecasting model. The simulated results of the idealized 2D and 3D street canyon experiments showed that the increment of PBL instability favored the downward transport of momentum from the upper flow above the roof to the pedestrian level within the street canyon. As a result, the flow and turbulent fields within the street canyon under the more unstable PBL condition are stronger. Therefore, more pollutants within the street canyon would be removed by the stronger advection and turbulent diffusion processes under the unstable PBL condition. On the contrary, more pollutants would be concentrated in the street canyon under the stable PBL condition. In addition, the simulations of the realistic building cluster experiments showed that the density of buildings was a crucial factor determining the dynamic effects of the PBL structure on the flow patterns. The momentum field within a denser building configuration was mostly transported from the upper flow, and was more sensitive to the PBL structures than that of the sparser building configuration. Finally, it was recommended to use the Mellor-Yamada-Nakanishi-Niino (MYNN) PBL scheme, which can explicitly output the needed turbulent variables, to provide the boundary conditions to the CFD simulation.
authors.affiliation: Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China. Electronic address: miaoyucong@yeah.net.
authors.forename: Yucong
authors.initials: Y
authors.lastname: Miao
authors.affiliation: Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China. Electronic address: lshuhua@pku.edu.cn.
authors.forename: Shuhua
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Yijia
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China; International Center of Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
authors.forename: Zhenxin
authors.initials: Z
authors.lastname: Liu
authors.affiliation: National Meteorological Center, China Meteorological Administration, Beijing 100081, China.
authors.forename: Bihui
authors.initials: B
authors.lastname: Zhang
mesh_terms: D000392:Air Movements; D000393:Air Pollutants / Q000032:analysis*; D001108:Architecture; D001272:Atmosphere / Q000032:analysis*; D002681:China; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D008962:Models, Theoretical; D014507:Urbanization; D014887:Weather
chemical_list: D000393:Air Pollutants
keywords: Computational Fluid Dynamics; Dispersion; OpenFOAM; Planetary Boundary Layer; Weather Researching and Forecasting model