Author(s)

Naraine Persaud, Moustafa Elrashidi, Xiaobo Zhou, Xining Zhao, Xiaoli Chen

Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, USA.
Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, USA.
Institute of Water Saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, China.
Natural Resources Conservation Service, Lincoln, USA.

Seasonal distribution of mono-modal, monsoonal rainfall across the semi-arid ecotone of sub-Saharan of West Africa is highly variable and unpredictable. The ever-present risk of drought and crop failure in this environment often results in food shortages that are met by emergency food aid. Humanitarian assistance planners would be better prepared for such interventions in a timely manner if they have reliable indicators that forewarn the impending failure of the rains. A good indicator would be a characteristic of the seasonal rainfall distribution that can be shown to be reasonably invariant over time and space. The objective of this study is to investigate whether such invariance existed for the seasonal median date (meaning the date when 50% of the seasonal total occurs). Such invariance is expected since the sun’s cyclic declination forces the advance and retreat of the Inter-tropical Front over West Africa. We examined the statistical properties of the seasonal median date for 1349 station-years of rainfall records for 30 rainfall stations in Burkina Faso and Niger with coordinates ranging from 9.88° to 18.5° north latitude and -4.77° to 13.2° longitude. The results showed that the median date was quite narrowly distributed over years with rather weak dependence on geographical coordinates. It can therefore be used as a reasonable ex-ante indicator of the success or failure of the rains as the rainy season progress.

Inter-Tropical Front; Inter-Tropical Convergence Zone; Semi-Arid Rainfall Prediction; Humanitarian Food Assistance; Food Insecurity; Semi-Arid Tropics; Niger; Burkina Faso

N. Persaud, M. Elrashidi, X. Zhou, X. Zhao and X. Chen, "Invariance in the Seasonal Median Dates for Mono-Modal Monsoonal Rainfall Distribution over the Semi-Arid Ecotone of Sub-Saharan West Africa," International Journal of Geosciences, Vol. 4 No. 6B, 2013, pp. 1-7. doi: 10.4236/ijg.2013.46A2001.