GIEWS > Data & Tools > Earth Observation
Earth Observation
The country level maps and graphs depict the latest 36-month period of the seasonal, vegetation and precipitation indicators. The data is presented by dekad and month   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.
Mexico
 

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.
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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.
  First DekadSecond DekadThird Dekad
 
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   

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.
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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.
  First DekadSecond DekadThird Dekad
 
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   

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.
 
2016 2015 2014
2013 2012 2011
2010 2009 2008
2007 2006 2005
2004 2003 2002
2001 2000 1999
1998 1997 1996
1995 1994 1993
1992 1991 1990
1989 1988 1987
1986 1985 1984
1983 1982

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.
 
2016 2015 2014
2013 2012 2011
2010 2009 2008
2007 2006 2005
2004 2003 2002
2001 2000 1999
1998 1997 1996
1995 1994 1993
1992 1991 1990
1989 1988 1987
1986 1985 1984
1983 1982

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, while a low and/or negative NDVI value would indicate 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.
 First DekadSecond DekadThird Dekad  Monthly