- © GFZ
Recent improvements in the development of VLBI (Very Long Baseline Interferometry) and other space geodetic techniques like GNSS require for different tasks a priori information of short period (daily and sub-daily) Earth rotation variation. One significant contribution to Earth rotation variation on this time scale is caused by diurnal and semidiurnal ocean tides. The IERS (International Earth Rotation and Reference System Service) conventional model for the short period ocean tidal variations in Earth rotation was evaluated by different groups and they highlight the need for an updated model.
In cooperation between TU Vienna, TU Berlin, GFZ Potsdam and DGFI at the TU Munich, this project aims to develop and evaluate an alternative model for short period ocean tidal Earth rotation variation. This improved model is based on an ocean tide model (EOT11a), considering multi-mission satellite altimeter observations since 1992. By use of a solely observational based model of ocean tides, this approach become independent from the assimilation of altimeter observations into hydro- dynamic ocean models. On the other hand, it is necessary to determine tidal velocities from heights of ocean tides by a simplified inversion approach.
In the past, modeling of high-frequency ocean tidal Earth rotation variation was an issue, where the ocean tide modeling and was independent from Earth rotation modeling. Within the project SPOT we develop an alternative model, where the ocean tidal angular momentum model and the Earth rotation variation is set up jointly. The close collaboration of experts in satellite altimetry based ocean tide models, Earth rotation modeling and VLBI analysis has provided the basis for this jointly approach. Beside the model of the short-period variation of the Earth’s rotation parameter (ERP), based on the ocean tide model EOT11a, we developed also ERP models, which consider alternatively ocean tide model FES2012 and HAMTIDE. Furthermore, we have assessed the effect of uncertainties in the elastic Earth model on resulting ERP models. Our proposed alternative ERP model to the IERS conventional model considers the elastic model PREM and 260 partial tides.
For the time interval January 2010 to December 2013 VLBI analysis considering the different a-priory models of short-period ocean tidal Earth rotation variation with and without estimation of the ERP is conducted to evaluate the a-priory models. The SPOT model performs in terms of WRMS (weighted root-mean squares) similar to the IERS conventional model.
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- Böhm, J., Krasna, H., Böhm, S., Choliy, V., Hellerschmied, A., Hofmeister, A., McCallum, J., Karbon, M., Madzak, M., Mayer, D., Nilsson, T., Plank, L., Shabala, S., Soja, B., Sun, J. and Teke, K.: Vienna VLBI Software (VieVS): Current Status and Future Plans. IVS 2014 General Meeting Proceedings, Science Press, Beijing, China, ISBN 978-7-03-042974-2, 2014.
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