热带大气平均环流的纬向不均匀性和Kelvin波的动力作用

The Zonal Asymmetry of the Tropical Mean Circulation and the Dynamic Effect of Kelvin Wave

本文利用一个包含Ｗａｖｅ－ＣＩＳＫ机制以及蒸发、感热与扰动风场的反馈机制，并引入实际的下垫面温度分布和海陆差异的热带大气模式，较好地模拟了低纬平均环流在风场、散度场及低层位势高度场上的纬向非均匀性。分析表明这种纬向非对称性是由于下垫面的热力非均匀性造成的强迫与大气内部的热力－动力反馈过程相互作用的结果。对热力强迫的响应形成了西太平洋暖水区上的西风和东太平洋上的东风，而对简化模式的解析分析说明，由于热力－动力反馈造成的Ｋｅｌｖｉｎ波的发展过程。

A tropical β plane model which includes the wave CISK mechanism and the feedback of the perturbational wind with evaporation and sensible heating and which incorporates realistic underlying surface temperature distribution and land sea contrast is used to simulate the zonal non uniformity of the tropical mean circulation in wind field, divergence and low level potential height field. The result is in reasonable agreement with observations. Analyses show that this asymmetry is caused by the interaction of the forcing from thermally non uniform underlying surface with the internal feedback mechanism between thermal and dynamic processes in the tropical atmosphere. The response to thermal forcing gives rise to the westerlies over the western Pacific warm pool and the easterlies over the eastern Pacific. Moreover, further analyses with a simplified model demonstrated that the development processes of the Kelvin wave due to thermal dynamic feedback may explain the fact that the easterlies are stronger than the westerlies.