For the period 1931 to 1996 rainfall station data was used to calculate (interpolation using kriging) the rainfall over West Africa for each month. The annual rainfall was then caluclated as the sum of the rainfall over 12 months. The number of active stations between 1931 and 1996 varies, but is always at least 30. Rainfall from June 1995 onwards was downloaded for 10-day (dekad) periods from FEWS-ADDS. To estimate rainfall, FEWS uses satellite information of cold cloud duration (CCD) from the Geostationary Operational Environment Satellite (GOES). The CCD estimate is adjusted using available rain gauge data, topography, relative humidity, wind direction and terrain slope. The FEWS data was used to calculate annual rainfall 1996 - 2004. To see rainfall for individual years click on the time-table below the map.