Evaporation From rain‐wetted forest in relation to canopy wetness, canopy cover, and net radiation

Abstract

Abstract. Evaporation from wet canopies is commonly calculated using E pM , the Penman-Monteith equation with zero surface resistance. However, several observations show a lower evaporation from rain-wetted forest. Possible causes for the difference between E pM and experiments are evaluated to provide rules for the simulation of rainfall interception by forest canopies. The evaluation is executed using a micrometeorological model with a detailed representation of the forest canopy. Simulated results are compared with experimental results. In spite of theoretical reservations the evaporation of completely wet forest appears to agree with EpM. Evaporation from wet forest appears mainly dependent on net radiation. Rainfall interception is related to evaporation from the canopy. Evaporation from the canopy appears proportional with the square root of canopy cover and sensitive to canopy wetness. An accurate estimate of canopy wetness is needed to use E pM for the calculation of evaporation from rain-wetted forest.

Edge effects and forest water use: A field study in a mixed deciduous woodland

“…In terms of the actual interception loss this is most likely to be compensated for by a reduced storage capacity near the edge . Alternatively, Klaassen (2001) suggested that incomplete canopy wetness is another possible reason for the limited effect of distance to the edge on throughfall. A two-dimensional examination, however, accounting for rain shadow effects, has not been carried out on woodland edges before.…”

Measurements and modeling of throughfall variability for five forest communities in the southeastern US

“…The intercepted precipitation evaporates without reaching the soil (Klaassen, 2001). Main factors influencing the interception are canopy storage capacity and wet canopy evaporation rate (Loustau et al, 1992).…”

A stochastic model of throughfall for extreme events

“…Of the processes involved in canopy interception, the bestdescribed is evaporation, where work has included processlevel investigations at small spatial and temporal scales (e.g. Rutter et al, 1971;Murphy and Knoerr, 1975;Gash et al, 1999;Klaassen, 2001) and development of models useful at larger spatial and temporal scales (e.g. Sellers et al, 1996;Ramírez and Senarath, 2000).…”

“…Murphy and Knoerr, 1975;Gash et al, 1999;Klaassen, 2001). Deterministic approaches to modelling evaporation by these processes have dominated the canopy interception literature (e.g.…”