Direct leaf wetness measurements and its numerical analysis using a multi-layer atmosphere-soil-vegetation model at a grassland site in pre-alpine region in Germany

Katata, Genki; Held, A.*; Mauder, M.*

The leaf wetness was monitored using electrical sensors directly clipped to living leaf surfaces of thin and broad-leaved grasses. The measurements were carried out at the pre-alpine grassland site in Germany from September 20 to November 8, 2013. Numerical simulations of a multi-layer atmosphere-SOiL-VEGetation model (SOLVEG) were carried out for analyzing the data. The model reproduced well the observed leaf wetness, surface fluxes and temperature, and soil temperature and moisture. In rain-free days, a typical diurnal cycle as a decrease and increase during the day- and night-time, respectively, was observed in leaf wetness data. The high wetness level was always monitored under rain, fog, and snowcover conditions. Leaf wetness was also often high in the early morning due to thawing of leaf surface water frozen during a cold night.