Machimura T., Nakai T., Okada K., Tanaka Y., Urano S., Horiguchi I. J. Agric. Meteorol 52- (5) 497 -500 1997
[Not refereed][Not invited] The decoupling theory presented by Jarvis and McNaughton (1986) was used in the comparison of the evapotranspiration characteristics of forest, corn and alfalfa canopies. The average values of the decoupling factor Ωc were 0.53, 0.74 and 0.88 in the forest, corn and alfalfa, respectively, which was in the opposite order for the aerodynamic roughness of the canopies. Ωc varied largely with the change of the canopy resistance. The Ωc indicated the variability of the ratio of the evapotranspiration to the available energy (lE/A). When Ωc<0.8, the reliability of the evapotranspiration models based on the available energy (e. g. Priestley-Taylor model) should decrease.