Rossby波的螺旋斑图

THE SPIRAL PATTERNS OF THE ROSSBY WAVES

应用描写大气大尺度运动的准地转方程组 ,求得了大气Rossby波的三维定常流场以及相应的位温场、涡度场和散度场 ,其中的三维流场构成了物理空间的一个非线性自治动力系统 .研究表明 ,Rossby波具有倾斜的螺旋结构 ,在流场槽前下层呈水平辐合和上升运动 ,而流场槽后是下沉运动和下层水平辐散 .在水平面上 ,这种倾斜的螺旋结构 ,使得西风动量自北向南和自南向北向Rossby波的中心区集中 ,产生Rossby波的“负黏性”现象 .基本西风气流和地球的旋转 ,对于Rossby波的螺旋结构的形成是十分重要的 .

Starting from the quasi-geostrophic motion equations describing the large-scale motion in the atmosphere, the steady three-dimension stream field and the corresponding potential temperature, vorticity and divergence fields are obtained. So the three-dimensional velocity field constructs a nonlinear autonomous dynamical system in the physical space. It is shown that the Rossby waves possess a tilting spiral structure, which represents that the stream field is horizontal convergence at lower layer and ascending motion in front of trough, but descending motion and horizontal divergence at lower layer behind the trough. It makes westerlies momentum from the north and the south concentrate on the center regions of Rossby waves, this is known ordinarily as the “negative viscosity” phenomena. It implies that the rotation of earth and basic current are playing an important role in the spiral structure of the Rossby waves.