Evapotranspiration Mapping in Google Earth Engine (SEBAL)

Identify cold anchor pixels from water bodies to estimate evapotranspiration and near-zero sensible heat, and hot anchor pixels in dry bare fields to map residual heat via surface temperature differences.

Open your Google Earth Engine profile, create a repository for the sebal model, upload the farmland shapefile, add country shapefiles, develop the net radiation flux script, and save.

Compute incoming shortwave radiation in Google Earth Engine using the solar constant, sun elevation, and atmospheric transmissivity, mapping a radiation band across the dataset with SEBAL.

Compute the outgoing longwave radiation using the Stefan-Boltzmann equation in Google Earth Engine, add it as a band with this name, and save after each step in the SEBAL workflow.

Export net radiation flux to Google Drive, download the TIFF rasters, and open them in ArcGIS or QGIS to analyze albedo, NDVI, SAVI, and temperature for evapotranspiration mapping.

Develop momentum roughness length for sensible heat flux within a Google Earth Engine workflow, using Copernicus land use land cover classification at 100 m to extract UAE class areas.

Import uncorrected momentum roughness lengths and net radiation flux into the Sebal script, define and clip study-area geometry with Copernicus land cover, and layer leaf area index for visualization.

Compute the grain ratio from ndvi, setting it to 0.5 if ndvi is negative, then derive soil heat flux G as grain ratio times net radiation, and compute Rn ratio.

Map a function over an image collection to create a feature collection, computing weather parameters and including day of year, year, minutes, temperature, surface radiation, wind, and dew point.

Compute daily evapotranspiration with SEBAL in Google Earth Engine by importing net radiation flux, wind speed, soil heat flux, and Landsat imagery, then derive correlations, boundaries, and ndvi-based estimates.

Compute instantaneous evapotranspiration and the transpiration fraction, then derive daily evapotranspiration using SEBAL in Google Earth Engine. Visualize results with color palettes, export maps, and repeat the workflow across images.