Department of Atmospheric Sciences;
Nanjing University;
Nangjing 210093 Institute of Urban Meteorology;
China Meteorological Administration;
Beijing 100089;
Department of Atmospheric Sciences;
Nanjing University;
Nangjing 210093ased on a pseudo-spectral large eddy simulation (LES) model;
an LES model with an anisotropy turbulent kinetic energy (TKE) closure model and an explicit multi-stage third-order Runge-Kutta scheme is established. The modeling and analysis show that the LES model can simulate the planetary boundary layer (PBL) with a uniform underlying surface under various stratifications very well. Then;
similar to the description of a forest canopy;
the drag term on momentum and the production term of TKE by subgrid city buildings are introduced into the LES equations to account for the area-averaged effect of the subgrid urban canopy elements and to simulate the meteorological fields of the urban boundary layer (UBL). Numerical experiments and comparison analysis show that: (1) the result from the LES of the UBL with a proposed formula for the drag coefficient is consistent and comparable with that from wind tunnel experiments and an urban subdomain scale model;
(2) due to the effect of urban buildings;
the wind velocity near the canopy is decreased;
turbulence is intensified;
TKE;
variance;
and momentum flux are increased;
the momentum and heat flux at the top of the PBL are increased;
and the development of the PBL is quickened;
(3) the height of the roughness sublayer (RS) of the actual city buildings is the maximum building height (1.5-3 times the mean building height);
and a constant flux layer (CFL) exists in the lower part of the UBL.;
城市边界层; 大旋涡仿真; 各向异性; 混乱动力能量关闭模型;