90 Days-Long Predictions of LoD and Polar Motion from Global Hydrodynamic Model Data

Short-term forecasts of effective angular momentum functions (EAM) due to (i) atmospheric dynamics, (ii) ocean general circulation, (iii) spatially variable barystatic sea-level, and (iv) terrestrial water storage variations are combined with least-squares extrapolation and auto-regressive modelling to routinely predict polar motion (PM) and Δ UT1 for up to 90 days into the future. Based on several experiments with more than 500 individual hindcasts scattered over the years 2016 - 2019, a best-performing parametrization for the method was identified. At forecast horizons of 10 days, the prediction accuracy is 3.02 mas and 5.39 mas for PM and Δ UT1, respectively, corresponding to improvements of 34% and 44% with respect to Bulletin A. At forecast horizons of 60 days, prediction accuracies are 12.52 mas and 107.96 mas for PM and Δ UT1, corresponding to improvements of 34% and 8% over Bulletin A. The 90 days-long EAM forecasts leading to those improved EOP predictions are routinely published at isdc.gfz-potsdam.de/esmdata at around 12 a.m. every day and are thus ready-for-use for operational EOP prediction efforts.