Climate Variation Dynamics of the Troposphere-Stratosphere Coupled System

本文采用理论方法、数值实验和资料分析等方法，研究了对流层-平流层耦合系统气候的形成过程及其变率机制。理论方法：开发了GFD数值库ISPACK，进行了数值实验，阐明了极涡变形和相关重力波辐射的参数依赖性。在纬向对称强迫的球形正压模式下，我们计算了极涡的时间演化过程，并确定了极涡以十几天为周期重复破坏和恢复的参数区。奇异值分析表明，误差增长与时间和位置有关。-数值实验：利用三维全球环流机制模式进行参数扫描实验，考察了太阳活动变化引起的赤道QBO和平流层顶附近温度变化对极地涡旋垂直耦合的影响。ep通量分析表明，平流层突然预警的发生频率和特征与这些参数的关系是由于行星波的传播特性发生了变化。-资料分析：利用SAGE-II卫星资料分析对流层上层和平流层下层背景气溶胶的变化。提取与季节或赤道QBO同步的变化分量，分析其特征。利用三维机制模式长时间积分获得的内部变率数据，利用全球/半球再分析数据对平流层低层降温趋势的可探测性进行了评估。结果表明，当数据长度限制在20年以内时，检测的可靠性仅在夏季超过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.