Anomaly Analysis of Evapotranspiration Worldwide

This dataset holds 25 years of worldwide monthly and annual raster maps of remote-sensed evapotranspiration (actual and potential). It includes aggregated values, average normals and anomalies related to a reference climatological epoch. Methods All monthly maps were retrieved from NASA's MODIS "MOD16A2GF" product via Google Earth Engine scripting. The 8-day period scenes were reduced to the mean considering calendar months and also upscaled to 10 km pixel resolution. Annual means, normals and the anomalies were computed via Python scripting and GDAL. Definitions: The normal epoch is a reference period in which samples are compared. A normal month (e.g., the normal January) is the mean of all calendar months under the normal epoch. The annual normal is the mean of all annual samples. The absolute anomaly of a given sample is the difference from the normal mean. The relative anomaly of a given sample is the percent difference from the normal mean. The z-score anomaly of a given sample is the ratio between the difference to the normal mean and the normal standard deviation. All calculations are performed via map algebra, ie, pixel-wise reductions. Source code: The avilable Python script "analysis_spatial_normals.py" provides the workflow of the anomaly analysis. Speficications Temporal range: 2000-02 to 2025-12 Normal epoch: 2001 to 2021 Coordinate Reference System: WGS 84 Raster format: GeoTiff Spatial resolution: ~10 km Pixel value for aggregated and normals = Evapotranspiration (mm). Pixel value for absolute anomaly = Evapotranspiration (mm). Pixel value for relative anomaly = Percent difference from the normal (%). Pixel value for z-score anomaly = Difference from the normal in standard deviations units (units of SD). Warning: pixel values are scaled by a scaling factor. Actual value = Pixel values / Scale factor The scale factor is encoded in the file name, as shown below. File name convention NASA_MODIS_{variable}_{variant}_{resolution}_{scalefactor}_{epoch}.tif Number convention 01K = 1000 01C = 100 010 = 10 Packages Files for Actual Evapotranspiration (AET) Annual scale AET_ANNUAL.zip -- archive with raster maps for annual values AET_ANNUAL_NORMALS.zip -- archive with raster maps for annual normal values AET_ANNUAL_ANOMALY-A.zip -- archive with raster maps for annual absolute anomaly values AET_ANNUAL_ANOMALY-R.zip -- archive with raster maps for annual relative anomaly values AET_ANNUAL_ANOMALY-Z.zip -- archive with raster maps for annual z-score anomaly values Monthly scale AET_MONTHLY.zip -- archive with raster maps for monthly values AET_MONTHLY_NORMALS.zip -- archive with raster maps for monthly normal values AET_MONTHLY_ANOMALY-A.zip -- archive with raster maps for monthly absolute anomaly values AET_MONTHLY_ANOMALY-R.zip -- archive with raster maps for monthly relative anomaly values AET_MONTHLY_ANOMALY-Z.zip -- archive with raster maps for monthly z-score anomaly values Files for Potential Evapotranspiration (PET) Annual scale PET_ANNUAL.zip -- archive with raster maps for annual values PET_ANNUAL_NORMALS.zip -- archive with raster maps for annual normal values PET_ANNUAL_ANOMALY-A.zip -- archive with raster maps for annual absolute anomaly values PET_ANNUAL_ANOMALY-R.zip -- archive with raster maps for annual relative anomaly values PET_ANNUAL_ANOMALY-Z.zip -- archive with raster maps for annual z-score anomaly values Monthly scale PET_MONTHLY.zip -- archive with raster maps for monthly values PET_MONTHLY_NORMALS.zip -- archive with raster maps for monthly normal values PET_MONTHLY_ANOMALY-A.zip -- archive with raster maps for monthly absolute anomaly values PET_MONTHLY_ANOMALY-R.zip -- archive with raster maps for monthly relative anomaly values PET_MONTHLY_ANOMALY-Z.zip -- archive with raster maps for monthly z-score anomaly values Versions 1.1.0 All version data available. Upload of Actual ET (AET) and Potential ET (PET) monthly packages. 1.0.1 Upload of Potential ET (PET) annual packages. 1.0.0 Upload of Actual ET (AET) annual packages. 0.0.0 Description and source code. Version naming convention v{Method Change}.{Major Change}.{Minor Change} Example: v1.2.4 Sources Running, S., Mu, Q., Zhao, M., & Moreno, A. (2021). MODIS/Terra Net Evapotranspiration Gap-Filled 8-Day L4 Global 500m SIN Grid V061 [Dataset]. NASA Land Processes Distributed Active Archive Center. https://doi.org/10.5067/MODIS/MOD16A2GF.061