Nonstationarity of meteorological baselines for atmospheric dispersion assessments: A 32-year dual-height case study at a nuclear facility site in South Korea

Atmospheric dispersion assessments at nuclear and industrial sites rely on location-specific meteorological baselines conventionally assumed to be stationary, although their stationarity under a changing climate and evolving land use has received little observational attention. Climate and land-use change may alter boundary-layer winds, thermal stratification, and atmospheric mixing, potentially reducing the representativeness of meteorological records used in environmental assessments. Using 32 years (1993–2024) of continuous observations at 10 and 67 m at the Korea Atomic Energy Research Institute in Daejeon, South Korea, we analyzed trends in a composite Dispersion Potential Index (DPI) proposed in this study and its underlying temperature, stability, and wind fields using Mann–Kendall tests and Theil–Sen slopes. Under a wind-speed filter ( ≥ 1.0 m s −1 ), the DPI increased significantly at both heights, indicating a nonstationary meteorological baseline. DPI tracked the regulatory dispersion factor χ / Q across 156 evaluation windows, while the 10-m wind-stilling signal was reproduced at six regional synoptic stations, including rural sites, indicating a coherent regional tendency rather than a single-site artifact. Logarithmic decomposition identified a mechanical wind-stilling pathway dominant at 10 m and a layer-averaged thermal stability pathway where the mechanical signal weakened at 67 m. Dual-height decomposition distinguished mechanical and thermal contributions that cannot be resolved from a single measurement height or a single-valued regulatory factor. These findings suggest that climate and land-use change may be altering dispersion-relevant baselines, with the surface response consistent with regional stilling and the elevated response consistent with broader warming.