Intraseasonal variations in the tropical Western Hemisphere and the generation mechanism of stratospheric Kelvin waves

利用基于球面原始方程组的数值模式研究了热带大气加热响应的四个问题。模式加热是作为一个外部强迫给出的。第一个问题是要澄清的作用，非定常性的反应，定常加热。为此，时间积分和平稳模型的构建。在定态解不稳定的参数范围内，两种模型的结果在异常场上显示出显著的差异。也就是说，从时间积分模型产生的时间平均值具有比稳态解更大的振幅。此外，从热带热源辐射的罗斯贝波列穿过中纬度，再次返回热带。因此，波的振幅变得很大，即使在区域远离热源。接下来，我们研究的热带-热带外相互作用的季节内变化的作用。该模型中的加热从60 E移动到180 ° C， ...更多信息 为期40天。当没有热带-热带外相互作用时，即，中纬度地区纬向平均气流较弱，仅在120 E中心热源附近季节内变化幅度较大。相反，当中纬度西风强时，从热带出发的波列穿过中纬度，返回热带。大气角动量（AAM）的变化也在同一模式中得到了检验。结果表明，与季节内变化有关的AAM的来源不是赤道地区，而是副热带地区。赤道地区是明显的来源，因为AAM从副热带输送到赤道。最后，通过数值试验验证了平流层Kelvin波是由西半球对流层季节内变化产生的假设。关于这一假说，我们至今还没有得到肯定的结果。少

Four problems about the atmospheric response to tropical heating were tackled using numerical models based on the primitive equations on the sphere. The model heating was given as an external forcing.The first problem is to clarify the role of nonstationarity in the response to stationary heating. For this purpose, time integration and stationary models are constructed. In parameter ranges for which stationary solutions are unstable, results from the both models show a significant difference in anomaly fields. That is, the time mean yielded from the time integration model has larger amplitudes than the stationary solution. Further, Rossby wavetrains radiating from the tropical heat source go through the midlatitude, again returning to the tropics. Thus, wave amplitudes become large even in regions which are far from the heat source.Next, we examine the role of the tropical-extratropical interaction in the intraseasonal variation. Heating in this model moves from 60E to 180ﾟ, having the … More period of 40days. When there is no tropical-extratropical interaction, i.e., the zonal mean flow in midlatitudes is weak, the amplitude of the intraseasonal variation is large only near the heat source centered 120E. In contrast, when the midlatitude westerly is strong, wavetrains starting from the tropics pass through the midlatitude, returning to the tropics. Then, the intraseasonal variation amplifies in the Western Hemisphere.Variations of the atmospheric angular momentum (AAM) are also examined in the same model. It is found that the source of the AAM associated with the intraseasonal variation does not lie in the equatorial region but the subtropics. The equatorial region is the apparent source, since the AAM is transported from the subtropics to the equator. It is also clarified that Rossby wavetrains play an important role in the acquisition and transportation of the AAM.Finally, numerical experiments are performed, in order to examine the hypothesis that stratospheric Kelvin waves are generated from the tropospheric intraseasonal variation in the Western Hemisphere. We have not so far obtained a positive result about this hypothesis. Less