Average wet canopy evaporation for a Sitka spruce forest derived using the eddy correlation-energy balance technique

Hourly measurements of evaporation of intercepted rainfall were made for six months in a Sitka spruce forest in Central Wales (UK) with an eddy-correlation system. Sensible heat flux was measured with a three-dimensional sonic anemometer mounted on a mast above the forest, and evaporation was solved as the residual in the energy balance equation. Hourly evaporation was also estimated with the Penman–Monteith equation, using the eddy-correlation measurements to estimate the aerodynamic conductance. Wind direction dependent differences in surface roughness caused the aerodynamic conductance to vary from 0.09 to 0.29 m s?1 at the average wind speed. Average measured (0.12 mm h^-1) and estimated (0.09 mm h^-1) wet canopy evaporation rates agreed reasonably well with a previously estimated Penman–Monteith value of 0.13 mm h^-1 for the same forest [J. Hydrol. 48 (1980) 89].