Short-term LOD and UT1-UTC forecast based on the Holt-Winters algorithm and angular momenta of global surficial geophysical fluids

This paper presents a novel hybrid method named HW-EZ for short-to medium-term forecasting of ΔLOD and UT1-UTC up to 90 days ahead. This method relies on the LOD time series with zonal tidal signals removed, the adaptive Holt-Winters (HW) additive algorithm, and the effective angular momentum (EAM) functions derived from global atmospheric, oceanic, and land water models. The dominant ΔLOD variations are estimated using EAM and tides, while the remaining ones are modeled by HW-EZ with an 8-year sliding window. Numerical validation shows that HW-EZ reduces UT1-UTC mean absolute error (MAE) by 13.77%-67.55% relative to IERS Bulletin A over 1-30-day forecasts. Using 6-day EAM forecasts maintains nearly equivalent accuracy. Comparisons with the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC) confirm that HW-EZ outperforms the average of more than 50 international methods and is competitive with state-of-the-art schemes. The HW-EZ method achieves robust ultra-short-term performance with UT1-UTC MAE ≤0.158 ms for 1-6-day forecasts, making it suitable for real-time geodetic and navigation applications.