The Dynamic Mechanism of the Formation of the Low Level Jet

The ordinary multidimensional reductive perturbation method is generalized so as to apply to the general case including the dissipative factor. With this the corresponding Cubic-Schr?dinger equation is deduced, and by the pre-liminary study of its solution, it shows that it is more admissible to consider atmospheric meso-scalc systems as the nonlinear Cubic-Schr?dinger waves. With suitable boundary and initial conditions, the Cubic-Schr?dinger equation is numerically integrated so as to investigate the possible dynamic mechanism as well as the impacts of the nonlinear action, turbulent friction and topography to the formation of the LLJ. The results indicate that the downward transfer of the momentum and the effect of the surface friction are responsible for the concentration of the momentum in the layer between 850 and 700 hPa. The location of the horizontal concentration of momentum depends on the propaga-tion of momentum, in the process the inertia-gravity internal wave is very important, whereas turbulent friction is unfavourable for or delays the formation of the low level jet.