Based on the scale analysis of the dynamic equations with the forcing factors the thermal and orographie forcings are found to be of a spatial scale effect. In case of the ULW scale the control action of these forcings can not be ignored and, consequently, the dynamic characteristics of the ULW differ significantly from those of long waves. Also, an ULW dynamic equations for forcings of variant intensities are presented.A qualitative study is made of the relations between the dynamic properties of ULW and the forcing actions such as the forcing effect on the vertical structure, quasi-steady feature, energy source for maintainance, and its evolution or catastrophe.