季节内尺度热带-中纬相互作用机制初探

本文使用一个简单的全球二层大气环流模式作了强迫响应数值试验。模式中引入了代表热带低频偶极型对流的异常强迫.结果表明这一强迫不仅能激发显著的局地大气响应,也能引起北半球中纬显著的低频异常波列,中纬波列的发展与热带强迫变化之间存在四分之一位相差关系.这些结果与观测研究的结果一致.进一步的分析表明,大气响应的位相滞后与强迫产生的能量从内模向外模的非线性转换过程有关.最后提出了季节内尺度热带-中纬相互作用的可能机制.

Preliminary Study on Mechanism of Tropical - Midlatitude Interaction on Intraseasonal Time Scale

Numerical experiments on forced response are carried out by a simple tow-level global atmospheric general circulation model. Anomalous forcing is introduced into the model, representing the tropical low-frequency dipole convective pattern. It is found that the forcing remarkably induces not only the local responses but also the low frequency anomalous wave trains in midlatitudes, and there is a one fourth phase difference between the midlatitude wave trains and the variation of the tropical forcing. These results are consistent with that of observational studies. Further investigation shows that the phase kg in atmospheric responses is related to the nonlinear transfer process of energy from internal mode to external mode generated by the forcing. Finally on the basis of above results, possible mechanism of tropi-cal- midlatitude interactions is proposed.