Naraine Persaud, Xiaobo Zhou, Moustafa Elrashidi
CSES Department, Virginia Polytechnic Institute and State University

 Rain fed subsistence agriculture is the livelihood for 90 % of the 75 million inhabitants of the semi-ari ecotone of sub-saharan of West Africa. The mono-modal rainfall distribution across this ecotone is highly variable and unpredictable with annual depth ranging from > 250 mm in the north to <1100 mm to the south. Many analyses of the point rainfall records for this eco-geographic region were aimed at uncovering reliable predictors of annual rainfall. The objective of this study was to examine the statistics of the median day of the annual rainfall distributions using decadal rainfall series for all stations with > 20 years of record in Burkina Faso and Niger (West African countries that straddle the semi-arid ecotone) between 9o 20' and 23o 30' north latitude. The results showed that the median date of the rainy season was quite narrowly distributed and therefore can be used as a reasonable predictor. However, its usefulness decreased with increasing latitude.