The Behavior of Passive and Buoyant Plumes in a Convective Boundary Layer, as Simulated with a Large-Eddy Model

Abstract

Abstract With a large-eddy model the large-scale flow structure of the convective boundary layer is simulated in a box of (5 × 5 × 2) km. The calculation is run till the turbulence has reached a quasi-steady state. At that time we introduce a line-source of contaminants and the calculation is continued with an additional equation for the concentration. We consider both passive and buoyant sources. The latter are simulated by increasing the temperature of the line-source with respect to the ambient temperature. We present data for two dimensionless release heights: zs/h = 0.15 and zs/h = 0.48. For a passive source our results agree well with the results of Willis and Deardorff and the results of the CONDORS experiments. With respect to a buoyant source we found that the influence of buoyancy on the plume parameters can be described in terms of the dimensionless buoyancy parameter F*; this conclusion is based on runs for F* = 0.01 and F* = 0.02. The simulations for buoyant plumes are compared with the labor...