摘要
根据非线性的动量方程,利用多时间尺度分析方法,探讨由经向扰动与纬向扰动相互作用在热带东风中所造成的一类正压不稳定。分析表明:在零级近似下,给出了两个扰动传播的频率表达式,在一级近似下,得到了两个零级扰动振幅的解析表达式。鉴于方程中散度项的存在,当不同尺度的三个波相作用而发生共振时,仅总动能守恒,而总位拟能不守恒,这一点与无辐散大气的结论不同。两种扰动动能相互转换的机制则是涡度场与散度场的相互作用。
Starting from the non-linear momentum equation and using the method of multipletime scales, this paper studies the barotropic instability due to the interaction between themeridional disturbance and the zonal disturbance in the tropical east wind field. The theoretical analysis shows that. Under the zeroth order approximation, we obtain the expression of two disturbance frequencies. Under the first order approximation, we also deduce the analytical expression of two amplitudes of zeroth order disturbance.Because of the existence of the divergence term in the equation, only the total kinetic energy conserves when three waves with different space scales take part in the resonant interaction, but the total potential enstrophy does not conserve. This result is different from that of a non-divergence atmosphere. The mechanism of exchange between the meridional disturbed kinetic energy and the zonal disturbed kinetic energy is the interaction between the vorticity field and the divergence field.
关键词
热带东风
经向扰动
纬向扰动
Tropical East Wind
meridional disturbance
zonal disturbance
vorticity field
divergence field
non-linear interaction
