The annual NDVI over the Sahel was taken from NOAA-AVHRR, and
calculated from reflectance in the near infrared (NIR)
and visible (VIS) regions:
NDVI = (NIR-VIS)/(NIR+VIS)
THe data used here is in 8 km resolution and was pre-processed by
the GIMMS (Global Inventory Monitoring and Modeling System)
group at NASA's Goddard Space Flight Center.
For each year the annual avearge NDVI was calculted from
dekad (10-day maximum) NDVI data.
To see rainfall for individual years click on the time-table below the map.
