NDVI-based Downscaling of the CREMAP Actual Evapotranspiration Maps

The increasingly used remote sensing-based evapotranspiration estimation techniques provide information about the spatial and temporal variability of evapotranspiration on the field and regional scales. For Hungary, the most reliable evapotranspiration mapping model is the CREMAP (Calibration-Free Evapotranspiration Mapping), which uses MODIS surface temperature data. The CREMAP evapotranspiration with its 1000×1000 m (1 km2) resolution can be used for examinations with larger scales, for example the comparison of the water balance of forests with different land cover types (agricultural areas, artificial surfaces, etc.). However, the 1 km2 spatial resolution is too coarse to be used for smaller scales like precision forest management or agroforestry systems. Therefore, a vegetation index-based (MODIS NDVI) downscaling process of the CREMAP evapotranspiration was developed, to a resolution of 250×250 m (6.25 hectares). The downscaling experiment was done for Hungary, for a drier (2003 May-October) and for a wetter (2005 May-October) period. The products were analyzed, according to forest stand types. The vegetation index-based evapotranspiration downscaling process can be used for getting hydrological data for forest resource management, climate change impact studies on smaller scales or agroforestry system research