Statistical and trend analyses of rainfall in Sokoto

Ismail Abubakar and *Oke Isaia

Abstract

Sokoto is in the North West geopolitical zone of Nigeria. The major occupation of the people in this city is farming, which depends on rainfalls. This article presents statistical and trend analyses of the rainfall in Sokoto. Rainfall data in the city for a period of 1915- 2008 were collected from archives. The existence of trend and sequence of rainfalls were established using non-parametric techniques. The study revealed that overall averages of yearly and monthly total rainfall were 726±24.03 mm and 61.75±25.31 mm respectively. Yearly total, mean, maximum and minimum rainfalls have Mann-Whitney of 42, 57, 67 and 37 between 1947and 1977 with 43, 66, 60 and 107 in the period between 1978 and 2008. Sen.’s estimator revealed that there are significant upward trends for yearly total (10.08mm/year), yearly mean (8.14 mm/year), maximum (6.84 mm/year) and minimum (10.72 mm/year) within a period of 1947 – 1977 and significant downward trends for yearly total (9.94mm/year), yearly mean (6.97 mm/year) and maximum (7.75 mm/year) within a period of 1978 – 2008. It was concluded that there is a significant downward trend in the yearly total and mean rainfalls at Sokoto in the last three decades (30years), which can be attributed to climate change.

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