Numerical study of dispersion in the convective boundary layer

Abstract

A simple one-dimensional turbulence model developed by Sun and Chang (1986a, J. clim. appl. Met. 25,1445–1453) is modified by including γ c (a reference potential temperature gradient) in the diffusion term of the heat equation to study the moist convective boundary layer. The results show that the stratification becomes neutral to slightly unstable in the middle and lower mixed layer but slightly stable in the upper mixed layer as observed, while the wind, moisture and eddy fluxes are very similar to those discussed by Sun and Chang. The results from the one-dimensional model are then applied to a two-dimensional dispersion model. The new concentrations are better than the previous results (Sun, 1986, Atmospheric Environment 20, 1877–1886). The ground level concentration, the mean height of concentration, and vertical speed simulated from this higher order closure model are also in good agreement with field experiments, water tank simulations and results obtained from the statistical models.