Spatiotemporal analysis of dry spells for support to agriculture adaptation efforts in the Sudano-Sahelian region of Nigeria

Change in rainfall pattern is one of the observed and projected impacts of climate change across the Sudano-Sahelian region of Nigeria. As a consequence, agricultural practices and water resources would highly be impacted. In this study, 38-year (1981-2018) daily rainfall data observed over 13 meteorological stations distributed across the Sudano-Sahelian region of Nigeria were used to investigate the spatial distribution and long-term trend of dry spells. Four dry spell indices defined as frequency of dry spell (FDS), total dry spell (TDS), maximum dry spell (MxDS) and mean dry spell (MDS) were examined monthly, focusing on the wet season (May-October). The results revealed a positive gradient in TDS, MxDS and MDS from southwest to northeast. In contrast, FDS revealed a negative southwest to northeast gradient. The highest TDS, MxDS and MDS days are found during wet season onset (May-June) and end of season (September-October), while the lowest days are found at the peak of the rainy season (July-August). Furthermore, an analysis of long-term trend using the nonparametric Mann-Kendall statistical test revealed a prevailing decline in TDS, MxDS and MDS from May to October. This could enhance agricultural activities over the region. However, a significant increase in dry spell is evident in Gombe (May-June) and Kaduna (June). This could pose a great threat to agricultural practices over these regions if it persists.