A Remote Sensing of ET Method Based on Surface Aerodynamic Temperature.

Spatially distributed crop evapotranspiration (ETc) using remote sensing (RS) inputs are needed to improve crop water management. An improved crop water management is becoming increasingly relevant because of the increasing competition for water from municipal, industrial, agricultural, recreational, environmental and other water uses. There are several remote sensing-based ETc methods published in the literature. These RS of ET methods vary in complexity and input data needs. However, a method is preferred if it is easier to apply and is reliable while yielding good estimates of spatial crop water consumption amounts. The RS of ET method has to perform well for a wide range of crop water use rates and irrigation strategies (i.e., full to limited irrigation).  In this study, crop ETc was estimated using a RS-based surface aerodynamic temperature model that can be applied using ground-, airborne-, or satellite-based multispectral images. The RS ET method also uses weather station data (i.e., air temperature, relative humidiy, and horizontal wind speed) and estimates of crop height and leaf area index. Results of crop water use estimates were evaluated using monolithic large precision weighing lysimeters. Results indicate that the method is reliable with an overall ET estimation accuracy larger than 85%. The RS, crop, environmental and micro-climatological conditions as well as the method accuracy and limitations are discussed.