The role of dew and radiation fog inputs in the local water cycling of a temperate grassland during dry spells in central Europe

Abstract. During dry spells, non-rainfall water (hereafter NRW) mostly formed from dew and fog potentially plays an increasingly important role in temperate grassland ecosystems with ongoing global warming. Dew radiation occur combination during clear calm nights, both use ambient vapor as a source. Research on the combined mechanisms involved NRW inputs to is rare, distillation of soil input pathway for formation has hardly been studied. Furthermore, eddy covariance (EC) measurements are associated large uncertainties clear, nights when occur. The aim this paper thus stable isotopes tracers investigate different pathways into Swiss at Chamau spells summer 2018. Stable provide additional information liquid (dew fog) that cannot be measured otherwise. We isotopic composition (δ18O, δ2H, d=δ2H-8⋅δ18O) vapor, droplets leaf surfaces, moisture them EC meteorological observations one dew-only two events. d was found strongly linked local surface relative humidity (r=-0.94), highlighting dominant source synoptic context studied spells. Detailed temporal evolution foliage signals suggest pathways: (1) downward through condensation (2) upward onto foliage. employed simple two-end-member mixing model using δ18O δ2H quantify these sources. With approach, we contributed 9 %–42 % total NRW, which compares well estimates derived near-surface vertical temperature gradient method proposed by Monteith 1957. produced 0.17–0.54 mm d−1 gain foliage, thereby constituting non-negligible flux canopy, compared evapotranspiration 2.7 d−1. Our results underline importance grasslands reveal complexity cycle such conditions, including inputs.