This study examines the length of the growing season in Nigeria using the daily rainfall data of Ikeja, Ondo, Ilorin, Kaduna and Kano. The data were collected from the archives of the Nigerian Meteorological Services, Oshodi, Lagos.

The Little Dry Season (LDS) of West Africa is manifested as a decline in both the frequency and amount of daily rainfall for a number of weeks halfway through the rainy season. The mean or climatological LDS is derived from the slope of the cumulative percentage graph of 5-day mean rainfall (daily rainfall data between 1961 and 2000). LDS variability analysis was carried out using the concept of relative variability. The results obtained showed that LDS is observed from mid-July to mid-September along the coast. Northward and eastward the period of occurrence decreases. In general, the phenomenon is not observed north of the eastward-flowing or east of the southward-flowing River Niger. The results also show considerable interannual variability. Variability was highest along the southwestern coast and declined inland northward and eastward. Variability was highest with respect to total rainfall, followed by length and number of rain days. There are indications that for most years the LDS was only relatively dry while in certain years it represented a period of drought. The occurrence of the LDS in space and time is explained by the movements of the intertropical discontinuity and its associated zone of rainfall. Interannual variability in occurrence and severity are determined by the Walker Circulation phenomenon. Variability in the severity of the LDS has mixed implications for agricultural practices.

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This study examined the sea surface temperature (SST) patterns in the Gulf of Guinea (GOG) and discussed their implications for the spatio-temporal variability of precipitation in West Africa. The SST data spanning over 49 years at 2°× 2°resolutions were sourced from the archive of the International Research Institute for climate prediction. The specific locations where data were collected to represent the GOG are longitudes 10°W, 8°W, 6°W, 4°W, 2°W, 0°, 2°E, 4°E, 6°E, and 8°E, and latitudes 5°N, 3°N, 1°N, 1°S, 3°S, and 5°S. The results obtained show that the SST in the GOG generally decreases westward and southward, while the reverse of the case holds for its variability values. Detailed observations show that the SST is generally below the latitudinal average and its variability values, above the latitudinal average mainly between longitudes 8°W and 2°E. The results also show that during the period of July-AugustSeptember, the SST is anomalously colder between longitudes 8°W and 2°E and the West African coastal border and latitude 3°N. This area was observed as constituting the area of the coastal upwelling. The intra-annual distribution of the SST, as evident along latitudes 3°N and 5°N, shows two main regimes and two transitional periods in between the regimes. The first regime is November to May, and the second, July to September. The first regime transits to the second during the month of June and the second back to the first, during the month of October. The comparative analysis of the first and second half of the period of study indicates that the SST of the GOG has undergone some warming over time. The comparison also shows that although the SST has generally risen, an area of relatively cool SST near the Guinea coast has expanded from longitudes 7°W-0°W to 8°W-3°E.

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The scientific evidence on rainfall variability with its significant impacts on crop yield is now stronger than ever. It is even more so on maize that serves as staple food in most parts of Sub-Sahara Africa. Hence, this study aim at examines and map spatio-temporal impacts of rainfall variability on water availability for maize yield using Geographic Information System (GIS). Major regions where maize is highly produced in Nigeria were selected and rainfall data for 30 years (1970 to 2000) were used for the Geospatial analysis. GIS Interpolation and other geospatial Analysis techniques were carried out to map the impacts of rainfall variability on maize yield. The results of the analysis and the maps produced show that inter-annual rainfall variability brings about the differences in water availability consequently affect the rate of maize yield in Nigeria.

The study developed a Geographical Information Systems (GIS) database and mapped inter-annual changes in tuber crop yield as a response to inter-annual rainfall variability in the Guinea Savanna ecological zone of Nigeria. It also related the spatiotemporal variability in rainfall with tuber yields. Two major tuber crops were used for this study (i.e. Cassava and Yam). Kriging and other GIS techniques were used for the spatial analysis. Also, correlation and regression analysis were carried out on the dataset. The study fund out that rainfall varies from one year to the other (550mm to 2987mm). The results showed that there were significant relationship between tuber yield and total rainfall (r= 0.68, at p<0.05 for cassava; and r= 0.62, at p<0.05 for yam). The study concluded that geospatial techniques are ample tools that should be explored further for realistic assessment of the effects on climate of farming activities.