By using the low-spectral model simplified from quasi-geostrophic approximation two-level model,we obtained the result that the equivalent barotropic state is an equilibrium state of the atmosphere in that model,and d...By using the low-spectral model simplified from quasi-geostrophic approximation two-level model,we obtained the result that the equivalent barotropic state is an equilibrium state of the atmosphere in that model,and discussed the conditions needed for existing the Rossby wave possessing the equivalent barotropic structure.And then we derived the oscillation equation reflecting the phase change of Rossby wave between higher and lower levels from the basic state of equivalent barotropic stationary Rossby wave,indicating the relations between the change of difference of phase at higher and lower levels and the disturbance of vertical shear,the amplitude disturbance of the part of waves of stream function and thermal wind stream function on the average level (A′ and B′).It is concluded that the inter-transformation exists between Rossby waves possessing the equivalent barotropic and baroclinic structure.展开更多
A two-dimensional,semi-geostrophic numerical model incorporating the tropopause and stratosphere is used to investigate the effects of a positive potential vorticity anomaly and latent heat release on the frontogeneti...A two-dimensional,semi-geostrophic numerical model incorporating the tropopause and stratosphere is used to investigate the effects of a positive potential vorticity anomaly and latent heat release on the frontogenetic process and the structure of the resulting frontal zone.It is demonstrated that(1)the inclusion of tropopause and stratosphere significantly changes the frontal structure only in the upper levels;(2)a clearly defined quasi-equivalent barotropic structure and a region of upward motion of finite width appear when a positive potential vorticity anomaly exists on the warm side of the maximum baroclinity in the lower troposphere,especially when it is located on the south edge of the baroclinic zone;(3)the above mentioned structure deteriorates as the frontogenesis proceeds in a dry atmosphere but can be maintained in a moist frontogenetic process with condensational heating;(4)the combination of a positive potential vorticity anomaly and the latent heat release is able to accelerate the frontogenesis significantly with the time needed to form an intense frontal zone reduced to less than 15 h.The results have significant theoretical importance in understanding the complex nature of frontal structure and frontogenesis,especially in understanding the dynamic structure of the subtropical frontal zone observed during early summer over East Asia.展开更多
文摘By using the low-spectral model simplified from quasi-geostrophic approximation two-level model,we obtained the result that the equivalent barotropic state is an equilibrium state of the atmosphere in that model,and discussed the conditions needed for existing the Rossby wave possessing the equivalent barotropic structure.And then we derived the oscillation equation reflecting the phase change of Rossby wave between higher and lower levels from the basic state of equivalent barotropic stationary Rossby wave,indicating the relations between the change of difference of phase at higher and lower levels and the disturbance of vertical shear,the amplitude disturbance of the part of waves of stream function and thermal wind stream function on the average level (A′ and B′).It is concluded that the inter-transformation exists between Rossby waves possessing the equivalent barotropic and baroclinic structure.
基金This research is supported by the National Natural Science Foundation of China.
文摘A two-dimensional,semi-geostrophic numerical model incorporating the tropopause and stratosphere is used to investigate the effects of a positive potential vorticity anomaly and latent heat release on the frontogenetic process and the structure of the resulting frontal zone.It is demonstrated that(1)the inclusion of tropopause and stratosphere significantly changes the frontal structure only in the upper levels;(2)a clearly defined quasi-equivalent barotropic structure and a region of upward motion of finite width appear when a positive potential vorticity anomaly exists on the warm side of the maximum baroclinity in the lower troposphere,especially when it is located on the south edge of the baroclinic zone;(3)the above mentioned structure deteriorates as the frontogenesis proceeds in a dry atmosphere but can be maintained in a moist frontogenetic process with condensational heating;(4)the combination of a positive potential vorticity anomaly and the latent heat release is able to accelerate the frontogenesis significantly with the time needed to form an intense frontal zone reduced to less than 15 h.The results have significant theoretical importance in understanding the complex nature of frontal structure and frontogenesis,especially in understanding the dynamic structure of the subtropical frontal zone observed during early summer over East Asia.
