Statistical Analysis of Extreme Rainfall Trends Events over Savanna Zones of Nigeria and its Possible Impacts

Abstract

ABSTRACT: This study analysed the trends id extreme rainfall of fourteen (14) synoptic stations in the savanna zones of Nigeria for the period of 35 years (1981-2015). The study acquired daily rainfall data from Environmental Management Programmed, Federal University of Technology Minna. The data was categories into seven extreme indices (heavy, very heavy, extremely heavy rainfall days, 1 –day annual maximum rainfall amount consecutive wet days annual maximum 1 rainfall amount to five 5 days annual maximum rainfall amount. Consecutive wet days and simple daily intensity indix by using ETCDI indices through RCI index software. Statistical tests of Mann Kendal (MK) based on a non-parametric approach was set for evaluate the possible trend in the derived indices. Results showed mixed trends of significant and insignificant in the seven selected extreme indices in some stations across the study area. Three stations (Bauchi, Kano and Katsina) Sadana savanna zones shows consisted significant increasing trends in most of the extreme indices while two stations (Abuja and Yola) showed consistent decreasing trends in most of the extreme indices; Generally, the results showed an increase in the occurrence of extreme rainfall events in the selected variables. The increase trends are possible pointer to climate change and a possible influencing factor to the frequent occurrence of flooding across the study areas.