Influence of Atmospheric Water Harvesting on Coupled Land Surface-Atmosphere Processes

Direct Air Capture (DAC) technologies designed for atmospheric water harvesting are increasingly being considered as a means of supplying water for green hydrogen production, particularly in arid and semi-arid regions. However, large-scale moisture removal from the atmosphere may affect the thermodynamics of the planetary boundary-layer, yet the magnitude and spatial characteristics of these impacts remain insufficiently characterized. In this study, we implement a physically based DAC parameterization within the ICOsahedral Nonhydrostatic (ICON) model, using Large-Eddy Simulation (LES) to explicitly resolve land–atmosphere exchange processes. DAC operation is represented as an imposed constant moisture extraction flux subtracted from the surface latent heat flux, with configurations spanning a range of flux densities (0–800 W/m) and deployment scales (4–900 units). Simulations reveal systematic near-surface warming and atmospheric drying associated with DAC operation. From the results High flux densities (>= 400 W/m^2)  1) reduce specific humidity of the local lower atmosphere by ~0.2 g/kg, and that of the land surface by 3.5 g/kg relative to the control, 2) decrease relative humidity by ~4 percentage points, 3) and increase virtual potential temperature by ~0.5 K with no significant regional effect. In addition, Large-scale deployments yield spatially distributed but cumulative effects both at the local and regional scale, producing domain-mean warming of ~0.5 K and specific humidity reductions of ~0.1–0.4 g/kg. These perturbations arise from suppressed evaporative cooling and reduced near-surface moisture availability, which may lead to modified local energy partitioning without fundamentally altering boundary-layer stability in the atmospheric boundary layer. For deployment densities above ~400 units, non-physical negative humidity values emerge, indicating that the extraction of moisture exceeds the atmospheric supply—a flux threshold for single unit DAC operation under the atmospheric conditions used here in the study. The results demonstrate that DAC-induced thermodynamic perturbations are non-negligible at both local and regional scales and can influence turbulent mixing, boundary-layer structure. This work provides a quantitative foundation for incorporating DAC into land-surface design, environmental regulation, and future deployment strategy for atmospheric water harvesting systems.