Numerical Studies on Time Variations of the Troposphere-Stratosphere Coupled System
Numerical Studies on Time Variations of the Troposphere-Stratosphere Coupled System
复制标题
对流层-平流层耦合系统时变的数值研究
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
Y. Naito
中科院分区：
文献类型：
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作者：
S. Yoden;M. Taguchi;Y. Naito
年际变化是一种年与年之间的变化，它被定义为一个气象量的气候年周期的偏离。它可以由大气循环系统的外部强迫的变化引起，也可以在系统内部产生。另一方面，季节内变化是一个季节内的低频变化，基本上被认为是内部过程的结果，即使在恒定的外部条件下也可能存在。本文介绍了极地平流层季节内和年际变化的一些观测事实，并系统地评述了利用一系列数值模式来了解平流层变化的情况。数值模式根据其复杂程度可以大致分为三类：简单低阶模式、中等机械环流模式和复杂大气环流模式。为了理解平流层变化，在“从属平流层变化”或“独立平流层变化”的假设下，使用了一系列只考虑平流层的模式。参数扫描实验是通过扫描控制参数的值来完成参数空间中的多次计算试验，是理解模型复杂行为的一种有效方法。然而，最近，对流层和平流层耦合变率对季节内和年际变化的重要性被指出。除了简单或复杂模式的数值研究外，我们还用三维机械环流模式进行了一些参数扫描试验，以了解对流层-平流层耦合变率。所有可能引起年际变化的外部强迫的影响都可以在数值试验中排除，只关注耦合系统内部产生的变化。所得到的季节内和年际变化在某些实际参数范围内具有与真实的大气相似的特征。讨论了外强迫年际变化的作用，指出即使在较小的振幅下，其作用也可能是显著的。
Interannual variation is a year-to-year variation which is defined as a deviation from the climatological annual cycle of a meteorological quantity. It can be caused by a variation of an external forcing of the atmospheric circulation system, or can be generated internally within the system. On the other hand, intraseasonal variation is a low-frequency variation within a season, and it is basically considered to be a result of internal processes which may exist even under constant external conditions. In this article, some observational facts on the intraseasonal and interannual variations of the polar stratosphere are presented, and the use of a hierarchy of numerical models to understand the stratospheric variations is reviewed systematically. Numerical models can be roughly divided into three classes based on their complexity; simple low-order models, medium mechanistic circulation models, and complex general circulation models. In order to understand the stratospheric variations, a hierarchy of stratosphere-only models have been used under an assumption of “slave stratospheric-variations” or “independent stratospheric-variations”. Parameter sweep experiment, in which many trials of computations in parameter space are done by sweeping the value of a control parameter, is a powerful method to understand complex behavior in the models. Recently, however, the importance of the coupled variability of the troposphere and the stratosphere was pointed out for the intraseasonal and interannual variations. In addition to numerical studies with simple or complex models, we have done some parameter sweep experiments with three-dimensional mechanistic circulation models to understand the troposphere-stratosphere coupled variability. All the effects of external forcings that might cause interannual variations can be excluded in the numerical experiments to focus only on internally generated variations within the coupled system. The obtained intraseasonal and interannual variations have some similar characteristics of the real atmosphere in some realistic parameter ranges. Roles of the interannual variations of the external forcings are discussed, which might be significant even if the amplitude is small.