Spatio-Temporal Analysis of the Rainfall Variability in the Derived Savannah Region of Nigeria, 1941 – 2010

Abstract

Studies have revealed evidence of rainfall variability and change in both trend and spatial patterns. Basic understanding of the long-term trend and spatial variation of rainfall distribution over a place for some periods of time would provide significant insight to the management and sustainable development of agriculture and other natural resources especially in a delicate environment like derived savannah. This study evaluates the spatial and temporal variability patterns of rainfall in the Derived Savannah region of Nigeria for the period between 1941 and 2010. The monthly rainfall data were acquired from the Nigerian Meteorological Services for six stations within and around the study area for the period. The data were standardized using a combination of standard deviation and mean, percentages of the coefficient of variation and temporal variability index were determined for each of the stations, which were interpolated using IDW techniques to generate surface maps so as to reveal the spatial and temporal patterns of rainfall. The study revealed that the mean annual rainfall increases at the rate of 1.20mm annually with a long term mean of 1,316mm and increasing in a north to south direction spatially. While the annual rainfall Coefficient of Variation (CV) varies between 8% and 38% and temporal variability indices range from -2.00 to 2.38 (i.e. from severely dry to extremely wet). The study shows there is a shift in Spatio-temporal distribution, pattern and trend due increased wetness and dryness in south and north respectively, there is a need for more climatic research in order to adopt appropriate adaptation and mitigation strategies.