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

我们将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，重新评估地球自转在日和亚日周期变化的相关激发机制。除了业务大气数据集外，还将纳入分辨率至少为3小时的再分析时间序列。我们的分析将主要基于欧洲中期天气预报中心（ECMWF）的数据，并由美国国家环境预测中心（NCEP）和美国国家航空航天局（NASA）的天气模型进行增强。为了明确地考虑海洋对亚日大气变化的动态响应，我们将利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。除了为所考虑的子系统建立单独的角动量变化外，我们将特别分析作用在大气、海洋和固体地球之间不同水平和横向边界上的扭矩。因此，我们的目的是在一个更好的理解所考虑的模型所代表的角动量的主要物理传输过程，并在同一时间试图彻底的数值验证的分析显示的角动量和扭矩的方法之间的等价性。虽然该项目的主要重点将是大气过程，但计划与世界海洋观测实验组织一起进行的实验将提供所考虑的时间尺度内海洋对角动量收支的贡献的估计，从而能够最终将模拟结果与观测到的地球自转在日周期和次日周期上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.