Abstract: The impacts of the intensity of capping inversion on the development of a super-thick convection boundary layer and the entrainment process in an arid area were simulated by large eddy simulation using intensive field observation data from Dunhuang, China. The results show that:（1）Before the capping inversion was broken, the weaker inversion was, the more unstable the mixed layer; the more favorable the turbulent vertical upward development; the thicker the convective boundary layer, mixed layer, and entrainment layer; and the greater the entrainment speed. Additionally, the entrainment effect was strong at the top of the boundary layer when the inversion was weaker. When the capping inversion layer was completely convective through the fully developed boundary layer, the boundary layer convection, which was originally confined to the strong overlying inversion layer with low thickness and high energy, the convection mixing was more intense, the entrainment was stronger, and the more likely it was that the mixed layer and the neutral layer above the inversion layer would mix to form a super-thick boundary layer.（2）Before the capping inversion was broken, the turbulent kinetic energy of the boundary layer was mainly provided by thermal buoyancy. After the capping inversion layer was broken, the shear production term in the mixing layer contributed the most to the turbulent kinetic energy of the boundary layer.

Key words: atmospheric boundary layer, intensity of capping inversion, super-thick convective boundary layer; entrainment, large eddy simulation