Model-Based Evaluation of Dew Condensation Potential Across Contrasting Climates Using Field Observations, ERA5, CORDEX, and Local Weather Data

Dew condensation on passive collectors can supplement water availability across different climates, but its prediction remains uncertain because condensation depends on both atmospheric conditions and collector properties. This study evaluated a physically based model of dew condensation potential (horizontal condenser surface) using field observations from four sites: Helsinki (Finland), Maktau (Kenya), Ajaccio (Corsica, France), and Bordeaux (France). Simulations were primarily driven by ERA5 reanalysis data, while on-site weather station data were used for sensitivity analysis where available. Near-future dew behavior at the European sites was further examined using EURO-CORDEX climate data. The model reproduced the general timing and cumulative progression of condensation, but predicted yields were generally greater than observed yields, especially at Helsinki and Maktau. The best agreement was obtained by Bordeaux, where the experimental setup closely matched the model assumptions. On-site weather stations data improved agreement, highlighting the importance of site-specific nocturnal conditions. CORDEX simulations showed clear site differences, with Bordeaux having the highest and most stable projected condensation potential, Ajaccio frequent but low-intensity condensation, and Helsinki lower annual totals but comparable yield per dew night. The results show that the model was useful for comparing relative condensation potential across climates and identifying dew seasons, but accurately estimating the harvestable dew requires better representation of collector properties such as geometry and surface.