Global characterisation of GNSS-PWV behaviour stratified by the Köppen-Geiger climate classification

Abstract In recent decades, the warming planet has been reshaping the Earth’s hydrological cycle, reinforcing the need for accurate monitoring of water vapour dynamics. While ground-based Global Navigation Satellite Systems (GNSS) atmospheric monitoring has emerged as a powerful tool for sensing water vapour, a systematic assessment of long-term precipitable water vapour (PWV) variability across distinct climate types remains rather limited. Here, we present a global characterisation of PWV behaviours by analysing homogeneous, quality-controlled records from 1124 globally distributed GNSS stations, each with over 16 years of observations, within the Köppen-Geiger climate classification system. PWV behaviours are examined hierarchically, from major climate categories to precipitation- and temperature-related codes and detailed full climate regimes. Results demonstrate that PWV exhibits robust seasonal phasing across all regimes, with summer maxima and winter minima, highlighting the dominant thermodynamic control on moisture-holding capacity. Precipitation seasonality and aridity impose additional, regime-dependent modulation. Importantly, the full-code analysis reveals a non-linear thermo-hydrological coupling. To be clear, moisture-sufficient climates allow the thermal potential to be fully expressed, whereas moisture-limited climates cap PWV levels even under intense heating. Furthermore, hemispheric harmonisation demonstrates global synchrony in these behaviours across equivalent climate types. Overall, the findings establish an observation-based benchmark for interpreting GNSS atmospheric parameters, evaluating humidity fields in global climate models, and informing future refinements of climate zonation systems for improved atmospheric modelling and monitoring.