Measurements of Wet Canopy Evaporation in Forests: A Review

Wet canopy evaporation () has been recognized as a significant component of total evapotranspiration, especially in forests and therefore it is critical to accurately assess to understand forest hydrological cycle. In this review, I focused on the measurement methods and evaluating the magnitudes of at diverse forest types (e.g., deciduous, coniferous, mixed, and rain forests). I also present the general issues to be considered for measurements. The commonly used measurement methods for include the water balance, energy balance, and the Penman-Monteith (PM) methods. The magnitudes of ranged from 5 to 54% of precipitation based on the literature review, showing a large variation even for a similar forest type possibly related to canopy structure, rainfall intensity, and other meteorological conditions. Therefore, it is difficult to draw a general conclusion on the contribution of to evapotranspiration from a particular forest type. Errors can arise from the measurements of precipitation (due to varying wind effect) and throughfall (due to spatial variability caused by canopy structure) for water balance method, the measurements of sensible heat flux and heat storage for energy balance method, and the estimation of aerodynamic conductance and unaccounted sensible heat advection for the PM method. For a reliable estimation of , the combination of ecohydrological and micrometeorological methods is recommended.