Climate Variation Dynamics of the Troposphere-Stratosphere Coupled System

本文采用理论分析、数值试验和资料分析等方法，研究了对流层-平流层耦合系统的气候形成过程及其变化机制。取得的主要结果如下：-理论方法：我们开发了一个用于GFD的数值库ISPACK，用来进行数值实验，以阐明极涡形变和相关重力波辐射的参数依赖性。我们计算了具有纬向对称强迫的球面正压模式中极涡的时间演变，并确定了极涡以几十天的周期重复破裂和恢复的参数区域。奇异值分析表明误差的增长与时间和位置有关。-数值实验：我们利用三维全球环流机制模式进行参数扫描实验，以考察由于太阳活动的变化而引起的赤道QBO和平流层顶附近温度变化对极涡垂直耦合的影响。资料分析：利用SAGE-II卫星资料分析了对流层上层和平流层下部背景气溶胶的变化。提取了与季节或赤道QBO同步的变化分量，利用全球/半球再分析资料，基于三维机制模式足够长的时间积分得到的内部变率数据，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年内，探测的可靠性才能超过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.