Vol.:(0123456789) 1 3 Model. Earth Syst. Environ. DOI 10.1007/s40808-017-0356-2 ORIGINAL ARTICLE Spatiotemporal trend analysis of changing rainfall characteristics in Guinea Savanna of Nigeria Luka Fitto Buba 1  · Nura Umar Kura 2,3  · John Bathrobas Dakagan 1   Received: 27 May 2017 / Accepted: 3 August 2017 © Springer International Publishing AG 2017 enable policy makers and general public particularly farmers to understand the rainfall variability so as to adapt strategies like irrigation schemes for food security. This work will also help government to establish more efective meteorological stations at micro level to have dense network of stations for more accurate results. Keywords Climate change · Rainfall · Variability · GIS · Guinea savanna · Nigeria Introduction The observed pattern of circulation connecting the tropics and subtropics, including the trade winds, tropical convec- tion, and subtropical deserts coupled with other concepts of general fuid circulation gives impetus to explanation of rainfall controlling mechanisms (WMO 2011). Character- istics of rainfall have been linked to physical climatology which best gives reasons for variation over time and space. In West Africa (4°–20°N; 20°W–40°E), annual rainfall declined since the end of the 1960s, 20–40% noted between the periods 1931–1960 and 1968–1990 (Chappell and Agnew 2004; Dai et al. 2004). Mean annual precipitation was reported to have decline by about 4% in the tropical rain-forest zone in West Africa, 3% in North Congo and 2% in South Congo between the periods of 1960–1998 (Malhi and Wright 2004). Contrary to this, an increase in annual rainfall by about 10% along the Guinea Coast during the last 30 years was also reported (Nicholson et al. 2000). In the past 3–4 decades, West African region underwent a notice- able decline in rainfall from 15 to 30% depending on the area (Niasse 2005). However, 1994 experience a high intensity of rainfall and was considered to be the wettest year of the said period (McCarthy et al. 2001). Abstract This study attempt to examine the changing rain- fall characteristics in Guinea Savanna of Nigeria. In view of the aim and targeted objectives, rainfall was carefully looked at on monthly and annual basis in brief and ecological spa- tial scales with data from 1980 to 2014. The study consid- ered 12 stations which represent the area. Basic descriptive statistics like the mean, standard deviation, coefcient of variation including other inferential statistics such as linear regression, and standardized anomaly were successfully uti- lized. Variables analyzed include monthly and annual rain- fall amount and number of rain days. Geostatistical analysis was employed mainly for spatial analysis in geographical information system (GIS) environment. Highest coefcient of variation of rainy days in Northern Guinea occurs in Yola 37% while highest in Ilorin in the Southern Guinea is 12.19%. The coefcient of determination (R 2 ) of annual rainfall amount and rainy days were 66, 56, 63, 73 and 41% for Ibi, Abuja, Lokoja, Makurdi and Lafa respectively. It was generally discovered that rainfall shows variation tem- porally. The high variations of rainfall at higher latitudes reveal the unreliable nature of rainfall as one progresses towards Northern Guinea and vice versa. This results will * Nura Umar Kura nuraumar@gmail.com Luka Fitto Buba lfbuba454@gmail.com John Bathrobas Dakagan hibathy2010@yahoo.com 1 Bayero University Kano, P.M.B 3011 BUK, Kano, Nigeria 2 Faculty of Environmental Studies, Universiti Putra Malaysia, UPM Serdang, 43400 Selangor, Malaysia 3 Department of Environmental Science, Federal University Dutse, P.M.B 7156 FUD Dutse, Jigawa, Nigeria