Down-scaling of Sebal Derived Evapotranspiration Maps

10 11 The major problem with high spatial resolution satellite images from Landsat 7 is that 12 imagery is not available very often (i.e. every 16 days or longer) and the coverage area is 13 relatively small (swath width 185km), while images of lower spatial resolution from MODIS are 14 available daily and one image covers a relatively large area (swath width 2,330km). This paper 15 considers the feasibility of applying various down-scaling methods to combine MODIS and 16 Landsat imagery in order to obtain both high temporal and high spatial resolution. The Surface 17 Energy Balance Algorithm for Land (SEBAL) was used to derive daily evapotranspiration (ET) 18 distributions from Landsat 7 and MODIS images. Two down-scaling procedures were evaluated: 19 input down-scaling and output down-scaling. In each down-scaling scheme, disaggregated 20 imagery was obtained by two different processes: subtraction and regression. The primary 21 objective of this study was to investigate the effect of the different down-scaling schemes on the 22 spatial distribution of SEBAL derived ET. We found that all of the four proposed down-scaling 23 methodologies can generate reasonable spatial patterns of the disaggregated ET map. The results 24