This map shows drought risk in the region by overlaying twenty years of data compiled and made available by UNEP/GRID.
Drought events: defined as areas where monthly precipitation is lower than 50% of the median value calculated for the period 1961 - 1990 during at least three consecutive months.
This method is adapted from Brad Lyon at the Columbia University - International Research Institute for climate Prediction (IRI). 1 Map of entire Africa;
Map data source: FAO, Global Discovery, UNEP/GRID, GAUL 2007, UNEP: http://www.grid.unep.ch/activities/earlywarning