A thermal-based remote sensing modelling system for estimating crop water use and stress from field to regional scales

Thermal-infrared remote sensing of land surface temperature provides valuable information for quantifying root-zone water availability, evapotranspiration (ET) and crop condition. A thermal-based scheme, called the Two-Source Energy Balance (TSEB) model, solves for the soil/substrate and canopy temperatures that achieve a balance in the radiation and turbulent heat flux exchange with the lower atmosphere for the soil/substrate and vegetation elements. In doing so, the TSEB is applicable to a wide range in atmospheric and canopy cover conditions. A modelling framework will be described called the Atmosphere-Land Exchange Inverse (ALEXI) that couples the TSEB scheme with an atmospheric boundary layer model in time-differencing mode to routinely map regional-scale daily ET at 3 to 10-km resolution using geostationary satellites. A related algorithm (DisALEXI) spatially disaggregates ALEXI output down to finer spatial scales using polar orbiting satellites. This modelling system along with strategies for fusing information from multiple satellite platforms and wavebands is being used to generate daily ET maps from field to regional scales. A summary of recent validation studies applying this multi-scale and multioral modelling system to experimental sites in agroecosystems will be presented.