Prediction of Universal Time (UT1) from Atmospheric Angular Momentum

Accurate positioning by satellite (GPS, GLONASS, DORIS) requires prediction of Universal Time UT1, as do systems of interplanetary spacecraft navigation. Below 10 days, the UT1 variations are mostly due to the exchange of angular momentum between the atmosphere and the crust. Therefore UT1 predictions at these time scales can be based on the predicted values of the axial Atmospheric Angular Momentum (AAM). Such values are derived daily by miscellaneous meterorological centers over the 5-10 forthcoming days. In the present study we characterize the quality of three current AAM forecasts, those of the U.S. National Centers for Environmental Prediction, the European Centre for Medium-Range Weather Forecasts, and the United Kingdown Meteorological Office. We analyze the associated prediction of UT1, especially compared to one determined without the use of any geophysical information, namely based classically on the EOP series history, and we check the skill of the current forecast procedure.