Thermal stratification of the atmospheric surface layer has strong impact on the land-atmosphere exchange of turbulent, heat, and pollutant fluxes. Few studies have been carried out for the interaction of the weakly to moderately stable stratified atmosphere and the urban canopy.  This study performs a large-eddy simulation of a modeled street canyon within a weakly to moderately stable atmosphere boundary layer. To better resolve the smaller eddy size resulted from the stable stratification, a higher spatial and temporal resolution is used.  The detailed flow structure and turbulence inside the street canyon are analyzed. The scaling law of velocity fluctuation above the street canyon is explored and compared with measurements. The relationship of pollutant dispersion and Richardson number of the atmosphere is investigated. Differences between these characteristics and those under neutral and unstable atmosphere boundary layer are emphasized. 

 

Li Xianxiang graduated from Tsinghua University in 2001 and 2004 with Bachelor and Master degrees, respectively. In 2008, he obtained his PhD degree from The University of Hong Kong. Then he joined Singapore-MIT Alliance for Research and Technology (SMART) as a postdoctoral associate. In 2011, he was promoted as Research Scientist.

His research interests include environmental (urban) fluid mechanics, urban climate, boundary-layer meteorology and atmospheric boundary layer. He has published (as first and corresponding author) more than 10 papers in top international journals in these fields, and serves as editors and reviewers for various international journals.