Africa - Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) Anomaly

Name: Africa - Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) Anomaly
Creator: African Center of Meteorological Applications for Development
License: http://www.opendefinition.org/licenses/cc-by

✦ DISCOVERED BY ORIONAIAfrican Center of Meteorological Applications for DevelopmentBiodiversityAfrica

Africa

About this dataset

The fAPAR Anomaly dataset maps deviations in vegetation health and photosynthetic activity across Africa. fAPAR measures the proportion of solar radiation absorbed by plants for photosynthesis, making it a robust biophysical indicator of vegetation status. The anomaly product highlights areas where vegetation activity is significantly below or above the long-term average, serving as a primary proxy for agricultural production and biomass availability. Unlike simple greenness indices (like NDVI), fAPAR is physically related to the energy and mass exchange processes of the canopy. Negative anomalies in this dataset are strong indicators of vegetation stress caused by drought, pests, or disease, making it a critical input for yield forecasting and food security analysis.

Documentation

This product is derived by comparing current satellite-observed fAPAR values against the long-term historical average for the same dekad or month. The resulting anomalies indicate whether the vegetation is performing better or worse than expected. It is frequently used as the "impact" component in combined drought indicators, confirming that meteorological deficits have translated into actual biophysical stress. Each ZIP download contains the original scanned TIFF files for a single calendar year, including monthly and dekadal scans. The files are provided in a ZIP archive to preserve the original sources and may be extracted and converted as needed. Cloud cover and atmospheric aerosols can sometimes interfere with optical satellite retrievals, although compositing techniques generally mitigate this. Extreme anomalies should be cross-referenced with rainfall or soil moisture data to confirm drought as the cause rather than non-climatic factors like land-use change or locust infestations.

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Africa - Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) Absolute Values

This dataset contains the absolute values of the Fraction of Absorbed Photosynthetically Active Radiation (fAPAR). While anomalies show deviations from the norm, these absolute values provide a direct measure of the current state of vegetation density and health. It represents the fraction of incoming solar radiation in the photosynthetically active spectrum that is absorbed by the canopy, ranging theoretically from 0 (bare soil) to 1 (dense, healthy vegetation). Absolute fAPAR is crucial for initializing crop growth models, estimating net primary productivity (NPP), and monitoring the phenological development of crops and natural vegetation throughout the growing season.

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Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) is a biophysical dimensionless quantity (its values range from 0/no absorption to 1/total absorption) used to assess the greenness and health of vegetation. FAPAR anomalies can be used as an indicator to detect and monitor the impacts of agricultural drought on the growth and productivity of vegetation. The data is presented in 10-day time composite of the Visible Infrared Imaging Radiometer Suite (VIIRS).

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