Atmospheric turbulence parameters characterization and seeing forecasting at the Daocheng site using ERA5 reanalysis data

ABSTRACT This study presents a comprehensive analysis of atmospheric parameters at the Daocheng site (100$^\circ 05^\prime$ E, 29$^\circ 08^\prime$ N) in China, using the ERA5 reanalysis data spanning 2014–2024. By implementing a physical parametrization scheme, we derive the vertical profiles of temperature, wind speed and optical turbulence strength, characterized by the refractive index structure constant $C_n^2(h)$. Our analysis reveals exceptional atmospheric stability, characterized by minimal tropopause height variations (range: 17.06–17.81 km; annual amplitude $<$0.74 km) and favourable summer conditions, with median 200 hPa wind speeds (V$_{200}$) remaining below 20 m s$^{-1}$ during June–September. The $C_n^2(h)$ profile decreases monotonically from the surface to approximately 11 km, followed by a pronounced peak near 17 km that is strongly correlated with the local thermal structure. The derived optical turbulence parameters demonstrate excellent median seeing conditions ($\varepsilon = 0.72\,\mathrm{ arcsec}$), with 25 per cent of values better than $0.48\,\mathrm{ arcsec}$, along with key parameters including atmospheric coherence length ($r_0 = 14.07$ cm), isoplanatic angle ($\theta _0 = 0.89\,\mathrm{ arcsec}$), and wavefront coherence time ($\tau _0 = 2.21$ ms). The atmospheric coherence length consistently exceeds 20 cm during summer months, significantly outperforming spring–winter transitions. Based on this analysis, we develop an integrated forecasting framework combining ARIMA and Holt–Winters methodologies to predict the excellent seeing conditions for 2025. Time series analysis confirms a robust seasonal pattern, quantified by a seasonal intensity coefficient of 0.771. This work provides systematic estimation and forecasting of atmospheric turbulence parameters at the Daocheng site, establishing crucial scientific foundations for atmospheric characterization, adaptive optics system design, and strategic planning of current and future telescope facilities.