Wave—CISK和低纬大气低频振荡

Wave-CISK and Low-Frequency Oscillation in the Tropical Atmosphere

本文运用一个包含Ｗａｖｅ—ＣＩＳＫ机制的斜压半地转模式来讨论低纬大气中的低频振荡。在我们以前研究工作的基础上，不仅考虑了ＣＩＳＫ机制的作用，而且考虑了ＣＩＳＫ机制垂直速度ｗＢ随纬度的变化。这样，建立的半地转模式和相应的解析解更能反映ＣＩＳＫ机制对低纬低频振荡的作用。在求解中，我们运用了本征函数Ｓｍ－３／２（Ｓｏｎｉｎｅ多项式）展开的方法，结果不仅得到了模式中所含的ＣＩＳＫ－Ｋｅｌｖｉｎ波和ＣＩＳＫ－Ｒｏｓｓｂｙ波波速与对流凝结潜热参数η的关系，而且显示了低纬高、低层大气间的相互耦合作用。在这样的低纬高、低层大气一定的对流凝结加热条件配合下，我们既获得了西传的ＣＩＳＫ－Ｋｅｌｖｉｎ波和ＣＩＳＫ－Ｒｏｓｓｂｙ波，又获得了缓慢东传的ＣＩＳＫ—Ｋｅｌｖｉｎ波和ＣＩＳＫ－Ｒｏｓｓｂｙ波，而且它们在一定条件下都可以出现不稳定。

A baroclinic semi-geostrophic model, including the wave-CISK mechanism, was established to analyse the low-frequency oscillation (LFO) in the tropical atmosphere. On the basis of our previous work, we not only considered the effect of CISK mechanism which was demonstrated as N2ηwB in the thermodynamic equation, but blso considered the variation of vertical velocity wB at the top of the boundary layer with the latitude. Under these considerations, the analytical solutions of equations which can describe the LFO in the tropical atmosphere are obtained, and the Kelvin waves and Rossby waves excited by the CISK mechanism, CISK-Kelvin. waves and CISK-Rossby waves, are discussed. It is shown that the wave-CISK mechanism is very important to the LFO in the tropical atmosphere. In this treatise we used the expansion in series of the eigenfunction S 3 /2(x) which was named as the Sonine polynomial. Among our results, we not only obtained the relationship between the propagating velocities of CISK-Kelvin waves and CISK-Rossby waves and the convective condensational heating parameter η, but also demonstrated the coupling effects for the upper and lower atmosphere in the tropics. It depends on the different values of η in the upper and lower atmosphere that the CISK-Kelvin waves and CISK-Rossby waves propagate eastWard or westWard, and these waves may be unstable.