Прогноз начала ледостава на примере реки Печоры в створе гидрологического поста Оксино

This study analyzes the applicability of L.G. Shulyakovsky's generally accepted methodology, developed in the second half of the 20th century, using in-situ hydrological observation data from 1980 to 2021 for the Pechora River at a hydrological station near the village of Oksino. Using meteorological observation data from the nearby Naryan-Mar meteorological station for the period 1950–2023, the study confirms a statistically significant warming trend in average annual air temperature (R² = 0.21). Using integral curve analysis, a "turning point" of 1999 was identified, marking the beginning of the stable phase of modern warming, based directly on data from the Naryan-Mar meteorological station; average temperatures since 1999 (–1.87 °C) are almost 1.7 °C higher than in the previous period (–3.53 °C). The basis of this work is the reconstruction of the average flow velocity–an important but unmeasured parameter during the autumn ice formation period–using a polynomial relationship between water level/discharge and average flow velocity (R² = 0.92 and 0.98, respectively), obtained from 125 field measurements over the observation period from 2015 to 2020. These relationships allow us to indirectly estimate the velocity on the day of first ice formation, which is then used in Shulyakovsky's formula to calculate the critical air temperature required for the formation of a stable ice jam. Over the entire verification period, the method achieved 62,5% H=f(u) and 67,5% Q=f(u) satisfactory forecasts, falling short of the 85% threshold established by the USSR Hydrometeorological Center. Forecast accuracy peaks at 100% for lead times of 3–5 and 9–13 days, provided no significant weather anomalies (e. g., prolonged thaws or abrupt cold spells) occur. Performance deteriorates markedly for lead times exceeding 14 days, with success rates dropping to 35,7–57,1% due to unaccounted meteorological extremes. The Q=f(u) relationship consistently outperforms H=f(u), primarily because tidal fluctuations in the Pechora estuary distort water level readings. The study confirms that Shulyakovsky’s method remains fundamentally applicable but requires regional recalibration of its empirical coefficients. A dynamic operational approach–featuring daily updates based on observed air temperatures–significantly improves forecast reliability, especially in years with extended ice formation periods. These findings support the method’s continued use in Arctic hydrometeorological practice, particularly for navigation safety and infrastructure planning in the context of climate change.