Anomaly Analysis of NDVI Worldwide

This dataset holds 25 years of worldwide monthly and annual raster maps of MODIS-derived Normalized Difference Vegetation Index (NDVI). It includes aggregated values, average normals and anomalies related to a reference climatological epoch. Methods All monthly maps were retrieved from MODIS "MOD13A3" product product via Google Earth Engine scripting. Annual means, normals and the anomalies were computed via Python scripting and GDAL. In the end, raster files were upscaled to 10 km. 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 script "analysis_spatial_normals.py" provides the rationale of the whole process. This script is mantained and updated on: https://github.com/iporepos/plans/blob/main/src/plans/tools/analysis_spatial_normals.py 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 = NDVI (unitless). Pixel value for absolute anomaly = NDVI (unitless). 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 Normalized Difference Vegetation Index (NDVI) Annual scale NDVI-10K_ANNUAL.zip -- archive with raster maps for annual values NDVI-10K_ANNUAL_NORMALS.zip -- archive with raster maps for annual normal values NDVI-10K_ANNUAL_ANOMALY-A.zip -- archive with raster maps for annual absolute anomaly values NDVI-10K_ANNUAL_ANOMALY-R.zip -- archive with raster maps for annual relative anomaly values NDVI-10K_ANNUAL_ANOMALY-Z.zip -- archive with raster maps for annual z-score anomaly values Monthly scale NDVI-10K_MONTHLY.zip -- archive with raster maps for monthly values NDVI-10K_MONTHLY_NORMALS.zip -- archive with raster maps for monthly normal values NDVI-10K_MONTHLY_ANOMALY-A.zip -- archive with raster maps for monthly absolute anomaly values NDVI-10K_MONTHLY_ANOMALY-R.zip -- archive with raster maps for monthly relative anomaly values NDVI-10K_MONTHLY_ANOMALY-Z.zip -- archive with raster maps for monthly z-score anomaly values Versions 0.0.0 Description and source code. Version naming convention v{Method Change}.{Major Change}.{Minor Change} Example: v1.2.4 Sources Didan, K. (2021). MODIS/Terra Vegetation Indices Monthly L3 Global 1km SIN Grid V061 [Dataset]. NASA Land Processes Distributed Active Archive Center. https://doi.org/10.5067/MODIS/MOD13A3.061 Date Accessed: 2026-09-25