线性准地转模型中副热带感热加热强迫的定常波

摘要

通过求取定常线性准地转位涡模式的解析解，研究了感热加热强迫所激发的副热带定常波的结构特征，讨论了基本流、牛顿冷却及地面摩擦等对定常波振幅和位相的影响。结果表明，东风时定常波在垂直方向上表现为上、下层反位相的第一斜压结构，且地面系统远强于中高层；西风时定常波呈现出向上的传播特征，在高层，随着风速增大振幅随高度的升高有增大趋势。在近地层，东风时气旋（反气旋）主体位于加热西（东）侧；西风时气旋（反气旋）主体位于加热东（西）侧，近地层以上相反。此外，发现东、西风基本流的作用具有对称特征，这与潜热加热显著不同。研究结果还表明，牛顿冷却对定常波有重要影响，基本流越弱影响越显著。在静止大气中，感热加热强迫下无斯韦尔德鲁普（Sverdrup）解，考虑牛顿冷却时，感热强迫在热源范围内的近地层和中高层分别激发出气旋式和反气旋式环流，气旋中心位于加热中心略偏西的位置。在非静止大气中，牛顿冷却项使地面系统中心向上风方向移动，东风时向东移。牛顿冷却对高、低层系统均有削弱作用。地面摩擦则明显不同，它总会使低层系统减弱，高层系统增强。%Analytical solutions of stationary waves forced by sensible heating in a linear quasi-geostrophic model are obtained and effects of the basic flow,the Newton cooling and surface friction on the amplitude and phase of stationary waves are dis-cussed.Results show that when the basic flow is easterly,the stationary waves exhibit a baroclinic structure in the vertical di-rection and the amplitude in the surface is stronger than in the middle and upper layer.When the basic flow is westerly,the waves propagate upward.In the lower layer,the cyclone (anticyclone)lies mainly to the west (east)of the heating center when the basic flow is easterly,and the cyclone (anticyclone)is located to the east (west)of the heating center when the basic flow is westerly.In the middle and upper layer,however,the opposite is true.It is found that the effects of the basic flow on the amplitude and phase of the waves are symmetric,which is different from the effects of condensation heating.The results also show that the Newton cooling has an important influence on the stationary waves especially when the basic flow is very weak. In a static atmosphere,the inviscid solution,i.e.the Sverdrup solution forced by sensible heating does not exist.When the Newton cooling is considered,the cyclone is forced in the lower layer and the anticyclone is forced in the middle and upper lay-ers within the area influenced by the sensible heating,and the center of the cyclone is located slightly to the west of the heating center.In a non-static atmosphere,the Newton cooling makes the centers of the surface systems move upwind.As a dissipative term,it weakens the system in both the lower and upper layers,which is different from the effects of surface friction.The sur-face friction always weakens the system in the lower layer and intensifies the system in the upper layer.