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Abstract:Estimation of evapotranspiration (ET) is of great significance in modeling the water and energy interactions between land and atmosphere. Negative correlation of surface temperature (T s ) versus vegetation index (VI) from remote sensing data provides diagnosis on the spatial pattern of surface soil moisture and ET. This study further examined the applicability of T s -VI triangle method with a newly developed edges determination technique in estimating regional evaporative fraction (EF) and ET at MODIS pixel scale through comparison with large aperture scintillometer (LAS) and high-level eddy covariance measurements collected at Changwu agro-ecological experiment station from late June to late October, 2009. An algorithm with merely land and atmosphere products from MODIS onboard Terra satellite was used to estimate the surface net radiation (R n ) and soil heat flux. In most cases, the estimated instantaneous R n was in good agreement with surface measurement with slight overestimation by 12 W/m 2 . Validation results from LAS measurement showed that the root mean square error is 0.097 for instantaneous EF, 48 W/m 2 for instantaneous sensible heat flux, and 30 W/m 2 for daily latent heat flux. This paper successfully presents a miniature of the overall capability of T s -VI triangle in estimating regional EF and ET from limited number of data. For a thorough interpretation, further comprehensive investigation needs to be done with more integration of remote sensing data and in-situ surface measurements.