Anomaly Analysis of Soil Moisture Worldwide

This dataset holds 10 years of worldwide monthly and annual raster maps of remote-sensed soil moisture fraction. It includes aggregated values, average normals and anomalies related to a reference climatological epoch. Methods All monthly maps were retrieved from SMAP Enhanced L3 Soil Moisture product via Google Earth Engine scripting. The weekly 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 absolute anomaly 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 Specifications Temporal range: 2015-03 to 2025-12 Normal epoch: 2015 to 2025 Coordinate Reference System: WGS 84 Raster format: GeoTiff Spatial resolution: ~10 km Pixel value for aggregated and normals = Soil Moisture Fraction (mm/mm). Pixel value for absolute anomaly = Soil Moisture Fraction (mm/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_SMAP_{variable}_{variant}_{resolution}_{scalefactor}_{epoch}.tif Number convention 01K = 1000 01C = 100 010 = 10 Packages Files for Soil Moisture (SM) Annual scale SM_ANNUAL.zip -- archive with raster maps for annual values SM_ANNUAL_NORMALS.zip -- archive with raster maps for annual normal values SM_ANNUAL_ANOMALY-A.zip -- archive with raster maps for annual absolute anomaly values SM_ANNUAL_ANOMALY-R.zip -- archive with raster maps for annual relative anomaly values SM_ANNUAL_ANOMALY-Z.zip -- archive with raster maps for annual z-score anomaly values Monthly scale SM_MONTHLY.zip -- archive with raster maps for monthly values SM_MONTHLY_NORMALS.zip -- archive with raster maps for monthly normal values SM_MONTHLY_ANOMALY-A.zip -- archive with raster maps for monthly absolute anomaly values SM_MONTHLY_ANOMALY-R.zip -- archive with raster maps for monthly relative anomaly values SM_MONTHLY_ANOMALY-Z.zip -- archive with raster maps for monthly z-score anomaly values Versions 1.0.5 Minor improvements in PDF preview visualization. 1.0.4 PDF preview visualization. 1.0.3 Upload preview visualization. 1.0.2 All version data is available. Upload of monthly values and monthly absolute anomalies packages. Edits in description. 1.0.1 Upload of monthly normals and anomalies packages (relative and z-scores). 1.0.0 Upload of annual packages. 0.0.0 Description and source code. Version naming convention v{Method Change}.{Major Change}.{Minor Change} Example: v1.2.4 Sources O'Neill, P. E., S. Chan, E. G. Njoku, T. Jackson, R. Bindlish, J. Chaubell, and A. Colliander. 2021. SMAP Enhanced L3 Radiometer Global and Polar Grid Daily 9 km EASE-Grid Soil Moisture, Version 5. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/4DQ54OUIJ9DL