热带对流层大气低频振荡机制的初步研究

A PRELIMINARY STUDY OF DYNAMICAL MECHANISM OF LOW-FREQUENCY OSCILLATION IN TROPICAL TROPOSPHERE

摘要:

本文从赤道β平面近似下的线性化扰动方程组出发,基于第二类条件不稳定(CISK)理论,研究了热带对流层大气准40天低频振荡的动力机制。研究发现,当对流层中、上层存在较大的对流凝结加热时可激发出纬向波数为1、周期为40天左右的不稳定Kelvin波,它以每天8到11个经度的相速缓慢向东移动。由此指出,观测到的热带对流层大气30—50天的低频振荡可能正是这种由对流凝结加热所驱动的缓慢东移的Kelvin波的具体表现。这可对热带对流层大气30—50天低频振荡现象的动力机制给以初步的物理解释。

Abstract:

In this paper, starting from the linearized primitive equations on the equatorial p-piane, the dynamical mechanism of intraseasonal oscillation (the so-called 30-50 day oscillation) in the tropical troposphere is investigated based on the CISK tneory.It is found that the unstable Kelvin wave with a zonal wavenum her 1 whose period is around 40 days and eastward phase speed is between 8 and 11 longitudes per day can be excited by preferred heating of cumulus convec ti ve condensation in the middle and upper troposphere.It is demonstrated that the observed intraseasonal oscillation in the tropical troposphere may be just the actual exhibitions of the Kelvin wave with a siow eastward propagation contrelled by the heating of cumuius convective conaensation.The results obtained here can give a primary physical explanation to the dynamical mechanism of the intraseasonal oscillation in the tropical troposphere.