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Seasonal Global Indicators
The seasonal indicators are designed to allow easy identification of areas of cropped land with a high likelihood of water stress (drought). The indices are based on remote sensing data of vegetation and land surface temperature combined with information on agricultural cropping cycles derived from historical data, and a global crop mask. The final maps highlight anomalous vegetation growth, and potential drought, in crop zones during the growing season.   More
The satellite data used in the calculation of the mean VHI and the ASI is the 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. The crop mask is a modified version of an EC-JRC data set that compiles several different sources of land cover data, including GlobCover V2.2, Corine-2000, AfriCover, SADC data set and USGS Cropland Use Intensity Data Set.
 
YearDekad
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Agricultural Stress Index  More
The Agricultural Stress Index (ASI) is an index based on the integration of the Vegetation Health Index (VHI) in two dimensions that are critical in the assessment of a drought event in agriculture: temporal and spatial. The first step of the ASI calculation is a temporal averaging of the VHI, assessing the intensity and duration of dry periods occurring during the crop cycle at pixel level. The second step determines the spatial extent of drought events by calculating the percentage of pixels in arable areas with a VHI value below 35 percent (this value was identified as a critical threshold in assessing the extent of drought in previous research by Kogan, 1995). Finally, each administrative area is classified according to its percentage of affected area to facilitate the quick interpretation of results by analysts.



Progress of Season  More
The Progress of Season depicts the development of the crop growing season. For any dekad in the year, the map indicates how far the season has progressed, represented by a value between 0 and 100 percent (i.e. 50 percent is the mid-point of the growing season). The seasons’ progress is based on the long-term average of vegetation phenologies for each pixel. This simplification implies that the crop phenologies are static and therefore the growing seasons progress at a constant rate each year.



Mean Vegetation Health Index  More
The mean VHI is an average of the dekadal VHI values over the crop growing season to date. The mean VHI is a good indicator of drought at pixel level. To facilitate analysis, the non-cropland is masked on the mean VHI maps.


 
YearDekad
Select:                        

Agricultural Stress Index  More
The Agricultural Stress Index (ASI) is an index based on the integration of the Vegetation Health Index (VHI) in two dimensions that are critical in the assessment of a drought event in agriculture: temporal and spatial. The first step of the ASI calculation is a temporal averaging of the VHI, assessing the intensity and duration of dry periods occurring during the crop cycle at pixel level. The second step determines the spatial extent of drought events by calculating the percentage of pixels in arable areas with a VHI value below 35 percent (this value was identified as a critical threshold in assessing the extent of drought in previous research by Kogan, 1995). Finally, each administrative area is classified according to its percentage of affected area to facilitate the quick interpretation of results by analysts.



Progress of Season  More
The Progress of Season depicts the development of the crop growing season. For any dekad in the year, the map indicates how far the season has progressed, represented by a value between 0 and 100 percent (i.e. 50 percent is the mid-point of the growing season). The seasons’ progress is based on the long-term average of vegetation phenologies for each pixel. This simplification implies that the crop phenologies are static and therefore the growing seasons progress at a constant rate each year.



Mean Vegetation Health Index  More
The mean VHI is an average of the dekadal VHI values over the crop growing season to date. The mean VHI is a good indicator of drought at pixel level. To facilitate analysis, the non-cropland is masked on the mean VHI maps.


Year
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Agricultural Stress Index   More
The Annual ASI depicts the percentage of arable land, within an administrative area, that has been affected by drought conditions over the entire cropping season. It differs from the ASI, which is based on conditions from the start of the season up to the current dekad.
 


Mean Vegetation Health Index

Year
Select:         

Agricultural Stress Index   More
The Annual ASI depicts the percentage of arable land, within an administrative area, that has been affected by drought conditions over the entire cropping season. It differs from the ASI, which is based on conditions from the start of the season up to the current dekad.
 


Mean Vegetation Health Index



Start of Season


End of Season




Start of Season


End of Season