A large-eddy simulation of a line source in a convective atmospheric boundary layer—I. Dispersion characteristics

Abstract

Abstract The dispersion of a passive line source in the convective atmospheric boundary layer is calculated with a large-eddy simulation. The results of the calculation are presented in the form of dispersion parameters. The total dispersion parameter is made up of two contributions: meandering and relative diffusion. Both contributions are calculated as a function of diffusion time and of source height. The results for vertical dispersion show that initially the contribution by meandering is large. Furthermore, the meandering component becomes larger as source height increases. These results can be interpreted in terms of the well-known looping plume in the convective boundary layer. The horizontal dispersion parameter is also influenced by meandering. However, in this case the lowest source has the largest meandering component. Finally, we consider the velocity statistics and demonstrate that they are consistent with the dispersion parameters.