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

热带西半球季节内变化与平流层开尔文波的产生机制

基本信息

批准号：
03640385
负责人：
ITOH Hisanori
金额：
$ 0.9万
依托单位：
Wakayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

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

使用基于球体原始方程的数值模型解决了有关大气对热带加热的响应的四个问题。模型加热作为外部强迫给出。第一个问题是阐明非平稳性在稳态加热响应中的作用。为此，构建了时间积分和平稳模型。在稳态解不稳定的参数范围内，两个模型的结果显示异常场存在显着差异。也就是说，从时间积分模型产生的时间均值具有比稳态解更大的幅度。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，即使在远离热源的区域，波幅也会变大。接下来，我们研究热带-温带相互作用在季节内变化中的作用。该模型的加热温度从 60°E 升至 180°C，持续时间为 40 天。当没有热带-温带相互作用，即中纬度纬向平均流量较弱时，仅在以120E为中心的热源附近季节内变化幅度较大。相反，当中纬度西风较强时，从热带地区出发的波列经过中纬度地区，返回热带地区。然后，西半球的季节内变化放大。在同一模型中还研究了大气角动量（AAM）的变化。研究发现，与季节内变化相关的AAM源头不在赤道地区，而是在副热带地区。赤道地区是明显的来源，因为 AAM 是从亚热带传输到赤道的。还阐明了罗斯贝波列在AAM的获取和传输中发挥着重要作用。最后，进行了数值实验，以验证平流层开尔文波是由西半球对流层季节内变化产生的假设。到目前为止，我们还没有获得关于这一假设的积极结果。较少的