Wave coupling processes of the middle and upper atmosphere: Interannual and long-term variability

高层大气的长期变化受底层大气动力过程的影响。这些气象影响主要是由于大气波从低层大气传播到热层。它们转移能量和动量，改变热层和电离层参数。大气波动不仅反映了中低层大气的动力学特征，而且呈现出长期趋势。因此，不仅众所周知的温室气体冷却对热层的长期变化有贡献，而且大气波动趋势也是如此，高层大气趋势的综合描述必须包括这种波动的变异性和趋势。为了量化低层和中层大气波耦合对高层大气动力学的影响，VACILT旨在观测、模拟和严格量化高层大气中低层大气波的年际和长期变化及其影响。为此，将对长期(30年)雷达观测的波浪和平均环流趋势进行分析。这些分析将与长期、低层大气驱动的盖亚地球系统模型模拟的结果进行比较，后者将得到热层观测分析的支持。根据盖亚的分析，低层大气由于波动对热层的强迫将被量化。这种强迫的可变性将在大气可变性较低的情况下确定和解释。为了证实这一结果，将进行机械模型的灵敏度实验。VACILT的主要目标是：(1)在地面和卫星观测的支持下，通过分析地球系统模式的平均环流和波动参数，定量描述中高层大气和热层的年际和长期变化和趋势；(2)定量估计高层大气中波耦合的程度；(3)综合分析中高层大气波耦合在强迫高层大气长期趋势和变化方面的作用，以及与温室气体冷却等其他驱动因素有关的作用。这些目标的实现将澄清低层大气强迫对高层大气变率的作用，直接有助于电离层建模和预测，而电离层建模和预测与现代通信和导航系统的性能密切相关。VACILT的研究将由德国莱比锡气象研究所的莱比锡大学、德国库朗斯伯恩的莱布尼茨大气物理研究所和日本九州大学的地球和行星科学系联合进行。这将把长期雷达观测和机械模型资源(德国)和地球系统模型资源和全球卫星观测资源(日本)结合起来，有效相辅相成，实现项目目标。

The long-term variations of the upper atmosphere are influenced by dynamical processes in the underlying atmosphere. These meteorological influences are mainly due to atmospheric waves propagating from the lower atmosphere to the thermosphere. Transferring energy and momentum, they modify thermospheric and ionospheric parameters. Atmospheric waves not only reflect dynamical features of the lower/middle atmosphere, but also exhibit long-term trends. Consequently, not only the widely known greenhouse gas cooling contributes to thermospheric long-term changes, but atmospheric wave trends also, and a comprehensive description of upper atmosphere trends will have to include this wave variability and trends.To quantify the effect of lower and middle atmosphere wave coupling on upper atmosphere dynamics, VACILT aims at observing, modeling, and rigorously quantifying interannual and long-term changes of lower and middle atmosphere waves and their effects in the upper atmosphere. To this end, long-term (> 30 years) radar observations will be analyzed with respect to waves and mean circulation trends. These analyses will be compared with results of a long-term, lower atmosphere driven simulation of the GAIA Earth System Model, which in turn will be supported by the analysis of thermospheric observations. From the GAIA analyses, the lower atmosphere forcing on the thermosphere due to waves will be quantified. The variability of this forcing will be determined and interpreted in the context of lower atmosphere variability. To substantiate the results, sensitivity experiments with a mechanistic model will be performed. Main goals of VACILT are (1) a quantitative description of interannual and long-term variability and trends in the middle atmosphere and thermosphere by analyzing the mean circulation and wave parameters from Earth System Model, supported by ground-based and satellite observations (2) quantitative estimates of the degree of wave coupling effects in the upper atmosphere (3) a comprehensive analysis of the role of middle-upper atmosphere wave coupling in forcing upper atmosphere long-term trends and variations, in relation to other drivers like greenhouse gas cooling. The achievement of these goals will clarify the role of lower atmosphere forcing on the upper atmosphere variability, directly contributing to ionospheric modelling and prediction which is closely related to performances of modern communication and navigation systems. The research within VACILT will be performed jointly by Universität Leipzig, Institute for Meteorology, Leipzig, Germany, Leibniz-Institute of Atmospheric Physics, Kühlungsborn, Germany, and Department of Earth and Planetary Sciences, Kyushu University, Japan. This will bring together resources of long-term radar observations and mechanistic models (Germany) and Earth system modelling and global satellite observations (Japan), which complements each other effectively to reach the project goal.