Improved 90-day Earth orientation predictions from angular momentum forecasts of atmosphere, ocean, and terrestrial hydrosphere

Short-term forecasts of atmospheric, oceanic, and hydrological effective angular momentum functions (EAM) of Earth rotation excitation are combined with least-squares extrapolation and autoregressive modeling to routinely predict polar motion (PM) and UT1 for up to 90 days into the future. Based on hindcast experiments covering the years 2016 and 2017, a best performing parametrization was elaborated. At forecast horizons of 10 days, remaining prediction errors are 3.02 and 5.39 mas for PM and UT1, respectively, corresponding to improvements of 34.5 and 44.7% when compared to predictions reported routinely in Bulletin A of the International Earth Rotation and Reference Systems Service. At forecast horizons of 60 days, prediction errors are 12.52 and 107.96 mas for PM and UT1, corresponding to improvements of 34.5 and 8.2% over Bulletin A. The 90-day-long EAM forecasts leading to those improved EOP predictions are routinely published on a daily basis at isdc.gfz-potsdam.de/esmdata/eam.