Comparison of ECMWF Reanalysis V5 (ERA5)-Based C n 2 Vertical Profiles with the Standard Hufnagel–Valley (HV) 5/7 Model

The performance of free-space optical (FSO) communication links depends strongly on the strength of atmospheric turbulence along the propagation path, quantified by the refractive-index structure parameter, Cn2 . The standard Hufnagel–Valley (HV) 5/7 profile is widely used as a baseline for comparing optical systems, but its fixed ground-level Cn2 and wind-speed inputs do not represent the actual atmospheric conditions of a given region or season. This study derives ground-level Cn2 and 5–20 km root-mean-square (RMS) wind speed for the Korean Peninsula and surrounding area (33.5–42.5°N, 124.5–131.5°E) from ECMWF Reanalysis V5 (ERA5) reanalysis data for 2015–2024, and applies these inputs to the HV model to build a grid- and month-resolved Cn2 vertical-profile database. Ground-level Cn2 shows a clear spatial contrast between mountainous and non-mountainous areas, while Cn2 aloft follows the seasonal cycle of RMS wind speed. To translate these differences into optical performance, the fried parameter r0 and split-step Fourier beam-propagation simulations were computed for a 1,550 nm, 300 km vertical satellite uplink. The winter profile yields r0 = 7.60 cm, much smaller than 28.22 cm for HV 5/7, with about three times larger RMS beam wander and a receiver-coupling efficiency roughly one-third that of HV 5/7. These results show that predicted receiver performance can vary substantially depending on the Cn2 profile applied, even under identical transmitter–receiver conditions. Rather than proposing a new standard to replace HV 5/7, this study offers a quantitative basis for assessing how region- and season-specific atmospheric conditions affect laser propagation performance.