Climate Variation Dynamics of the Troposphere-Stratosphere Coupled System

本文通过理论分析、数值试验和资料分析，研究了对流层-平流层耦合系统的气候形成过程及其变率机制。我们得到的主要结果如下：-理论方法：我们开发了GFD的数值库ISPACK，进行数值试验，以阐明极涡的变形和相关的重力波辐射的参数依赖性，我们计算了一个球正压模式与纬向对称强迫的极涡的时间演变，并确定了一个参数区，在该参数区中，极涡重复崩溃和恢复的周期为几十天。奇异值分析表明，误差增长取决于时间和位置。数值试验：利用三维全球环流机制模式进行了参数扫描试验，研究了赤道QBO和太阳活动引起的平流层顶附近温度变化对极涡垂直耦合的影响。EP-通量分析表明，平流层突发警报的发生频率和特征对参数的依赖性是由于行星波传播特性的改变。资料分析：利用SAGE-Ⅱ卫星资料分析了对流层上部和平流层下部背景气溶胶的变化。提取了与季节或赤道QBO同步的变率分量，分析了它们的特征，并利用全球/半球再分析资料，在三维机制模式足够长时间积分得到的内部变率资料的基础上，评估了平流层低层冷却趋势的可探测性。结果表明，只有在夏季，如果数据长度限制在20年，检测的可靠性超过95%。

We have investigated the formation process of climate of the troposphere-stratosphere coupled system and the mechanism of its variability by means of theoretical approaches, numerical experiments, and data analyses. The main results we obtained are as follows:- Theoretical approaches:We developed ISPACK, a numerical library for GFD, to conduct numerical experiments to clarify a parameter dependence of the deformation of the polar vortex and associated gravity wave radiation.We computed time-evolutions of a polar vortex in a spherical barotropic model with a zonally symmetric forcing, and identified a parameter region in which the polar vortex repeats breakdown and recovery with a period of several ten days. Singular value analyses revealed that the error growth depends on the time and the location.- Numerical experiments:We conducted parameter-sweep experiments using a 3-dimensional global circulation mechanistic model to examine the influence of both the equatorial QBO and the temperature variations near the stratopause due to the change of the solar activity on the vertical coupling of the polar vortex. The EP-flux analyses revealed that the dependence of the occurring frequency and the characteristics of the stratospheric sudden warnings on the parameters is due to a change of the propagation property of planetary waves.- Data analyses:The variations of the background aerosols in the upper troposphere and the lower stratosphere were analyzed using SAGE-II satellite data. Variation components synchronized with either the season or the equatorial QBO were extracted to examine their characteristics.The detectability of the cooling trend in the lower stratosphere were evaluated using global/hemispheric re-analysis data on the basis of the internal variability data obtained by long enough time integrations of a 3-dimensional mechanistic model. It was shown that the reliability of the detection exceeds 95% only in summer if the data length is limited to 20 years.