Evapotranspiration Estimation Using Energy Balance Algorithm for Pyramid-Based Spatially Enhanced Thermal Infrared Image

Evapotranspiration (ET) can be calculated indirectly from the surface temperature by means of energy balance approach. The surface temperature is derived from the thermal infrared bands (TIR) of the remote sensing data. Due to the coarse resolution of TIR band compared to visible bands, the ET estimates are limited to the spatial resolution of thermal band. This causes the current ET estimates of little use for analyzing its spatial distribution. This study adopts a multi resolution technique (Enhanced Laplacian Pyramid) for spatially enhancing the low resolution TIR band with the high pass details derived from the high spatial resolution visible band. The surface temperature images were computed from the original TIR and spatially enhanced TIR image. The surface energy balance approach is conducted for the original TIR image and spatially enhanced TIR image along with the other energy balance terms derived from visible bands. The energy fluxes and evapotranspiration images are also generated. Evapotranspiration values for the cropped area estimated using original TIR image and spatially enhanced TIR image were found to be 2.5 mm/day and 3.85 mm/day respectively. The estimated evapotranspiration are compared with evapotranspiration (2.8 mm/day) computed from CROPWAT model.