INTERPRETATION OF SURFACE TEMPERATURE/VEGETATION INDEX SPACE FOR EVAPOTRANSPIRATION ESTIMATION FROM SVAT MODELING

Evapotranspiration (ET) is one of the most significant components in the water and energy transfer between land surface and atmosphere at regional and global scales. this study aims to explore the underlying mechanism in the surface temperature versus fractional vegetation cover (T-s-F-r) space for regional ET and evaporative fraction (EF) estimation through a physically-based soil-vegetation-atmosphere transfer (SVAT) simulation. It also investigates the effect of vegetation type and physiology on the relationship between EF and T-s under deep-layer water-saturated and water-stressed conditions. The preliminary results show that in the T-s-F-r space surface EF varies linearly with surface temperature when root zone layer is not water-stressed. However, the linear relationship may be different between one vegetation type and another. When root zone layer is water-stressed, the variation of root zone layer soil water content has a negligible effect on the canopy temperature but the EF can be significantly influenced.