Global evaluation of Pandonia Global Network total column water vapour using co-located AERONET and GRUAN observations

Improving measurements of atmospheric water vapour remains a priority for the atmospheric science community, including for evaluation of satellite retrievals. The Pandonia Global Network (PGN) provides long-term, high-temporal-resolution direct-sun observations of total-column water vapour at many sites worldwide, but the PGN H₂O product has not yet been widely assessed against independent ground-based datasets across diverse conditions.

Here we present preliminary intercomparisons of PGN total-column water vapour with coincident AERONET sun-photometer retrievals at co-located sites, with additional context from comparisons to GRUAN-processed radiosonde profiles where available. We examine sensitivities to temporal matching and to factors such as solar zenith angle, season, and humidity regime and report initial network-wide and site-to-site statistics (bias, scatter, correlation).