KAPPA Framework — Paper 2 Supplementary Validation Data

Supplementary validation datasets (three-point vs. midpoint spatial sampling, ERA5 vs. IGRA2 radiosonde surface temperature comparison, dual gradient computation, and tropical radiosonde kappa comparison) for the manuscript 'Computing the Atmospheric Refraction Coefficient from ERA5 Reanalysis Data for Precision Levelling and Total-Station Survey'. All four datasets (S2, S3, S5, S7) are complete as of this record. See README.md for a description of two corrections made relative to an earlier draft of this data: an arithmetic error in the S7 tropical summary statistic, and a level-count error in the S5 dual-gradient summary that was also present in the manuscript's Supplementary Material and has been corrected there as well.