Spatiotemporal Analysis of Onset, Cessation and Length of Rainy Season in Benue State

Awoji Edwin, Peter Nkashi Agan, Adewale O. Adeyefa, Chioma Precious Oku

Article Under Review

This study evaluated the nature of onset, cessation and length of the rainy season in Makurdi, Otukpo, Gboko, Zaki-Biam, Igumale, Vandeikya, Katsina-Ala and Bopo stations in Benue state to unravel their trends. The earliest onset date for all stations fell in February while the actual onset date of rainfall in the state fell between March and April. The average onset coefficient of variability is 16.4% while the average CV for cessation and length of the rainy season is 3.04% and 6.87% respectively. The cessation date for rainfall season is between October and November and the rainy season lasts 6 to 7 months across all stations in the north and south of the state. Mann-Kendall trend test and Sen's Slope estimate used to test for trends in the onset and cessation dates and length of the rainy season for all stations revealed a significant upward trend in onset dates for Zaki-Biam and Bopo stations with p values of 0.04185 and 0.04512, an insignificant upward and downward trends in cessation dates of rainfall for all stations and significant downward trends in the mean length of the rainy season for Bopo and Zaki-Biam stations with p values of 0.003002 and 0.003623. Keywords: Onset date, Cessation date, Rainfall, Length of Rainy season, Trends etc.