Earth Observation
The vegetation indicators (NDVI anomaly, VCI and VHI) provide alternative measures of the relative vegetation health. These indices can be used to monitor the areas where vegetation may be stressed, as a proxy to detect potential drought. The precipitation indicators present a global analysis of the absolute (mm) and relative (%) rainfall levels per dekad, in addition to the long-term average precipitation levels (mm).   More
All three vegetation indicators are based on 10-day (dekadal) vegetation data from the METOP-AVHRR sensor at 1 km resolution (2007 and after). Data at 1 km resolution for the period 1984-2006 was derived from the NOAA-AVHRR dataset at 16 km resolution. Precipitation estimates for all African countries (except Cabo Verde and Mauritius) are taken from NOAA/FEWSNet, while for the remaining countries data is obtained from ECMWF.
DISCLAIMERS
The boundaries and names shown and the designations used on the maps do not imply the expression of any opinion whatsoever on the part of FAO concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers and boundaries.
YearDekad
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NDVI Anomaly  More
The Normalized Difference Vegetation Index (NDVI) measures the “greenness” of ground cover and is used as a proxy to indicate the density and health of vegetation. NDVI values range from +1 to -1, with high positive values corresponding to dense and healthy vegetation, and low and/or negative NDVI values indicating poor vegetation conditions or sparse vegetative cover. The NDVI anomaly indicates the variation of the current dekad to the long-term average, where a positive value (for example 20 percent) would signify enhanced vegetation conditions compared to the average, while a negative value (for instance -40 percent) would indicate comparatively poor vegetation conditions.


Vegetation Condition Index  More
The Vegetation Condition Index (VCI) evaluates the current vegetation health in comparison to the historical trends. The VCI relates current dekadal Normalized Difference Vegetation Index (NDVI) to its long-term minimum and maximum, normalized by the historical range of NDVI values for the same dekad. The VCI was designed to separate the weather-related component of the NDVI from the ecological element.


Vegetation Health Index  More
The Vegetation Health Index (VHI) illustrates the severity of drought based on the vegetation health and the influence of temperature on plant conditions. The VHI is a composite index and the elementary indicator used to compute the ASI. It combines both the Vegetation Condition Index (VCI) and the Temperature Condition Index (TCI). The TCI is calculated using a similar equation to the VCI, but relates the current temperature to the long-term maximum and minimum , as it is assumed that higher temperatures tend to cause a deterioration in vegetation conditions. A decrease in the VHI would, for example, indicate relatively poor vegetation conditions and warmer temperatures, signifying stressed vegetation conditions, and over a longer period would be indicative of drought. The VHI images are computed for the two main seasons and in three modalities: dekadal, monthly and annual.


YearDekad
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Estimated Precipitation  More
The map depicts cumulative rainfall volumes over a dekad (a 10-day period). Precipitation estimates are rainfall forecasts and are obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF).


Precipitation Anomaly


Estimated Precipitation (long term average)


YearMonth
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NDVI Anomaly  More
The Normalized Difference Vegetation Index (NDVI) measures the “greenness” of ground cover and is used as a proxy to indicate the density and health of vegetation. NDVI values range from +1 to -1, with high positive values corresponding to dense and healthy vegetation, and low and/or negative NDVI values indicating poor vegetation conditions or sparse vegetative cover. The NDVI anomaly indicates the variation of the current dekad to the long-term average, where a positive value (for example 20 percent) would signify enhanced vegetation conditions compared to the average, while a negative value (for instance -40 percent) would indicate comparatively poor vegetation conditions.


Vegetation Condition Index  More
The Vegetation Condition Index (VCI) evaluates the current vegetation health in comparison to the historical trends. The VCI relates current dekadal Normalized Difference Vegetation Index (NDVI) to its long-term minimum and maximum, normalized by the historical range of NDVI values for the same dekad. The VCI was designed to separate the weather-related component of the NDVI from the ecological element.


Vegetation Health Index  More
The Vegetation Health Index (VHI) illustrates the severity of drought based on the vegetation health and the influence of temperature on plant conditions. The VHI is a composite index and the elementary indicator used to compute the ASI. It combines both the Vegetation Condition Index (VCI) and the Temperature Condition Index (TCI). The TCI is calculated using a similar equation to the VCI, but relates the current temperature to the long-term maximum and minimum , as it is assumed that higher temperatures tend to cause a deterioration in vegetation conditions. A decrease in the VHI would, for example, indicate relatively poor vegetation conditions and warmer temperatures, signifying stressed vegetation conditions, and over a longer period would be indicative of drought. The VHI images are computed for the two main seasons and in three modalities: dekadal, monthly and annual.


YearMonth
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Estimated Precipitation  More
The map depicts cumulative rainfall volumes over a dekad (a 10-day period). Precipitation estimates are rainfall forecasts and are obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF).


Precipitation Anomaly  More
The map illustrates the difference between the current rainfall volume and the average level. Rainfall levels are compared with the Long-Term Average (LTA), which refers to the period 1989-2015. Warmer colours identify areas which have received lower-than-average rainfall, while colder colours are given to areas where precipitation has been above average.


Estimated Precipitation (long term average)



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Start of Season


End of Season