Remotely Sensed Evapotranspiration

Land surface evapotranspiration (E) is a key component of the water and energy balance over terrestrial ecosystems, quantification of which has long been an important topic in hydrological, meteorological, agricultural, and ecological studies. This chapter focuses on the quantification of E using remote sensing-based approaches, which provide a promising opportunity for spatially consistent and temporally continuous E mapping. An introduction of surface energy balance is firstly presented, followed by three typical methods of estimating E from remote sensing imageries (i.e., surface energy balance-based models, vegetation index-land surface temperature space models, and Penman-Monteith-based models) and the ETWatch model that combines the energy balance and Penman-Monteith models. A working example of comparing three remote sensing E models is then provided to better inform the model physics, as well as advantages and drawbacks. Additionally, temporal and spatial scaling methods are presented. Finally, existing terrestrial E products that have a global coverage and are publically accessible are introduced.