Atmosphere-Induced Short Period Variations of Earth Rotation (ASPIRE)

利用不同国际模拟中心提供的数值天气预报模式的高分辨率大气数据，我们将重新评估在日和次日周期变化的地球自转的相关激励机制。除业务大气数据集外，还将纳入至少3小时分辨率的再分析时间序列。我们的分析将主要基于欧洲中期天气预报中心（ECMWF）的数据，并辅以美国国家环境预测中心（NCEP）和美国国家航空航天局（NASA）的天气模型。为了明确考虑海洋对亚日大气变化的动态响应，我们将使用全球海洋环流和潮汐数值模式（OMCT）进行额外的实验，从而考虑到与地球自转日变化相关的所有地球物理流体的全球模式数据集。除了建立所考虑的子系统的单独角动量变化外，我们还将特别分析作用于大气、海洋和固体地球之间不同水平和横向边界的扭矩。因此，我们的目标是改进对所考虑的模型所代表的角动量的主要物理传递过程的理解，同时尝试对解析显示的角动量和扭矩方法之间的等效性进行彻底的数值验证。虽然这个项目的主要重点是大气过程，但与OMCT一起计划的实验将提供所考虑的时间尺度上海洋对角动量收支的贡献的估计，从而允许最终将模拟结果与观测到的地球自转在日和次日期间的非平稳变化进行比较。

By utilizing high-resolution atmospheric data from numerical weather prediction models provided by different international modelling centres, we will re-assess the relevant excitation mechanisms of the variable Earth rotation on diurnal and sub-diurnal periods. In addition to operational atmospheric data-sets, re-analysis time-series with at least 3-hourly resolution will be incorporated. Our analyses will be primarily based on data from the European Centre for Medium-Range Weather Forecasts (ECMWF), augmented by the U.S. weather models from the National Center for Environmental Prediction (NCEP) and the National Aeronautics and Space Agency (NASA). To take explicitly the dynamic response of the oceans to sub-daily atmospheric variations into account, we will perform additional experiments with the global numerical Ocean Model for Circulation and Tides (OMCT), thereby taking into consideration global model data-sets of all geophysical fluids that are relevant for diurnal variations of the Earth rotation.Besides establishing individual angular momentum variations for the sub-systems considered, we will in particular analyse torques acting at different horizontal and lateral boundaries between atmosphere, oceans, and the solid Earth. We thereby aim at an improved understanding of the dominating physical transfer processes of angular momentum as represented by the models considered, and at the same time attempt a thorough numerical validation of the analytically shown equivalence between the angular momentum and the torque approach. Although the main focus of this project will be on atmospheric processes, the experiments planned with OMCT will provide an estimate on the oceanic contributions to the angular momentum budget for the time-scales considered, thereby allowing to finally compare modelling results with observed non-stationary variations of Earth rotation on diurnal and sub-diurnal periods.