KAPPA Arc V5 — GFS κ Validation Dataset (Paper 4, Journal of Geodesy submission)

Raw validation datasets supporting the manuscript 'Real-Time Atmospheric Refraction Correction Using GFS Numerical Weather Prediction: Zero-Lag κ Computation for Operational Geodetic Applications', submitted to Journal of Geodesy. Files: gfs_validation.json (25 quality GFS–IGRA2 comparisons, 4 tropical stations), gfs_validation_v2.json (26 quality comparisons, expanded run including Nottingham), nottingham_gfs.json (6 quality Nottingham comparisons, altitude-corrected), saudi_gfs_validation.json (90 GFS-vs-ERA5 comparisons, Saudi Arabia; corrected in this deposit — see README.md for a boundary-value fix to the quality-comparison count and mean gap). These are the primary data underlying Tables 3–4 and Supplementary Sections S1–S4. This is a standalone deposit dedicated to Paper 4, separated from an earlier shared multi-paper record for clarity.