Evapotranspiration data obtained above various vegetated surfaces were analyzed. The amount of evapotranspiration E is depend on the meteorological parameters (radiation, air temperature, water vapor pressure, and wind speed), the ground surface parameters (vegetation type and leaf area index), and the precipitation amount. Since the potential evaporation EP(Kondo and Xu, 1997) represents the meteorological parameters, the non-dimensional evapotranspiration E/EP is investigated as functions of

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... he precipitation amount and leaf area index. The amplitude of seasonal cycle of E/EP is small for a typical Japanese basin composed of the evergreen and deciduous forests, but it is large for a deciduous forest and a grassland. The long-term mean of E /EP for several months increases as the precipitation amount increases. The dependence of E/EP on the leaf area index LAI is large for the forest, and it is small for the grassland. For the paddy field, on the other hand, E/EP is independent of LAI. For the forest, the value of E/Ep is from 0.1 to 0.2 when LAI=0, and from 0.7 to 0.8 when LAI> 5. For the grassland, the value is from 0.3 to 0.6 when LAI=0, and about 0.8 when LAI>2.