Assimilation of Earth Rotation and the Ocean's Circulation (EROC)
The project P2 (EROC) is part of the research unit "Earth Rotation and Global Dynamic Processes" and is funded by the German Research Foundation (FOR 584).
The Earth rotation parameters describe the state of Earth's rotation. Both, angular velocity as well as tilt of Earth's axis can be changed due to external torques and due to terrestrial mass movements. The latter is studied in this project with focus on the world oceans. Therefore, modern methods of data-assimilation (ensemble Kalman-Filters) are combined with global, numerical ocean modeling. Data-assimilation can make our ocean model (OMCT) consistent with the observed Earth rotation deviations (Fig. 1, red line). For this, knowledge about the other Earth-subsystems (like Atmosphere, Core, Mantle) has to be used. Data from respective models and reanalyses are used for this purpose. Afterwards, the comparison with a reference-simulation that does not assimilate data will be done (Fig. 1, black line). That way, physical, oceanic mechanisms which force the observed changes in Earth rotation can be identified. At least on the considered time-scales.
That signal-part of the Earth rotation observations that cannot be reproduced by the assimilated ocean model is also valuable. It contains information about the errors in the assumptions, the preprocessing, the model and the assimilation method. The project P2 is part of the research unit "Earth Rotation and Global Dynamic Processes". The research unit is funded by the German Research Foundation (FOR 584).
Reference:
Dill, R., Saynisch-Wagner, J., Irrgang, C., Thomas, M. (2021): Improving atmospheric angular momentum forecasts by machine learning. - Earth and Space Science, 8, 12, e2021EA002070. https://doi.org/10.1029/2021EA002070
Saynisch, J., Thomas, M. (2012): Ensemble Kalman-Filtering of Earth rotation observations with a global ocean model. - Journal of Geodynamics, 62, 24-29. https://doi.org/10.1016/j.jog.2011.10.003
Saynisch, J., Wenzel, M., Schröter, J. (2011): Assimilation of Earth rotation parameters into a global ocean model: excitation of polar motion. - Nonlinear Processes in Geophysics, 18, 5, 581-585. https://doi.org/10.5194/npg-18-581-2011
Saynisch, J., Wenzel, M., Schröter, J. (2011): Assimilation of Earth rotation parameters into a global ocean model: length of day excitation. - Journal of Geodesy, 85, 2, 67-73. https://doi.org/10.1007/s00190-010-0416-0
