The physical characteristics of mesoscale are analyzed, and results show that the unbalanced forced motion is the fundamental cause, which leads to the evolution of some important mesoscale weather systems. In this pa...The physical characteristics of mesoscale are analyzed, and results show that the unbalanced forced motion is the fundamental cause, which leads to the evolution of some important mesoscale weather systems. In this paper, an alternative asymptotic expansion method, which is quite different from the conventional Rossby-number expansion, is used to simplify the potential vorticity equation. And the quasi-balanced (QB) model based on nonlinear balance equation is derived. The QB model, which is in analogy with the quasi-geostrophic model, can describe the fundamental characteristics of the mesoscale accurately and may be used as the basis of theoretical studies on the mesoscale atmospheric dynamics.展开更多
New Reynolds' mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion ...New Reynolds' mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion with r 0 will increase depth of Ekman layer, reduce wind velocity in Ekman layer and produce a more satisfactory Ekman spiral lines fit the observed wind hodograph. The wind profile in the surface layer including tur-bulent dispersion is still logarithmic but the von Karman constant k is replaced by k1 = 1 -2/k, the wind increasesa little more rapidly with height.展开更多
文摘The physical characteristics of mesoscale are analyzed, and results show that the unbalanced forced motion is the fundamental cause, which leads to the evolution of some important mesoscale weather systems. In this paper, an alternative asymptotic expansion method, which is quite different from the conventional Rossby-number expansion, is used to simplify the potential vorticity equation. And the quasi-balanced (QB) model based on nonlinear balance equation is derived. The QB model, which is in analogy with the quasi-geostrophic model, can describe the fundamental characteristics of the mesoscale accurately and may be used as the basis of theoretical studies on the mesoscale atmospheric dynamics.
文摘New Reynolds' mean momentum equations including both turbulent viscosity and dispersion are used to analyze atmospheric balance motions of the planetary boundary layer. It is pointed out that turbulent dispersion with r 0 will increase depth of Ekman layer, reduce wind velocity in Ekman layer and produce a more satisfactory Ekman spiral lines fit the observed wind hodograph. The wind profile in the surface layer including tur-bulent dispersion is still logarithmic but the von Karman constant k is replaced by k1 = 1 -2/k, the wind increasesa little more rapidly with height.
