Comparative advantages of Large Aperture Scintillometer and Eddy Covariance instrument for measuring evapotranspiration in irrigated farmlands

Evapotranspiration (ET), a critical element of surface energy balance, plays an important role in the exchange of energy, mass and momentum in the soil-plant-atmosphere continuum. Large Aperture Scintillometer (LAS) is recent emerging instrument put on the ground to observe surface fluxes across pixel dimensions. This study validated the reliability of LAS observations with observation data from Eddy Covariance (EC) instruments. EC is the officially recognized and commonly used ET equipment in the Chinese Ecosystem Research Network (CERN). Heat flux was measured in summer maize fields via both LAS and EC at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences in August 2010 and compared. The results showed a significant consistency in both daily and monthly changes in heat flux measurements by LAS and EC. ET obtained from LAS was almost consistent with that from EC (R²=0.800 4) at the monthly scale. However, some differences existed in the daily change probably due to the effects of underlying principles, environment conditions and measurement scale. The study suggested that surface water and heat flux data collected via LAS was reliable and applicable in verifying estimated ET via remote sensing.