ANALYSIS AND CHARACTERIZATION OF RAINFALL IN NIGERIA

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Date
1992-08
Authors
EKEMEZIE, ELIZABETH A.
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Abstract
v ABSTRACT An examination of rainfall characteristics in Nigeria and an attempt at regionalization of annual rainfall using the widely accepted technigue of principal component analysis have been made in this study. The study was based on rainfall records for the period 1901 - 1984, at forty stations distributed all over the country. The Swed and Eisenhart's runs test indicated that with the exception of Ibi, the series for the stations were homogeneous. The standardised coefficients of skewness and kurtosis, and the chi-square test showed that the series for 80% of the stations were normally distributed. The Mann- Kendall Rank test indicated that 75% of the stations were influenced by random processes, and that the randomness did not exhibit any regional patterns. However, the remaining 25% showed downward trends which appeared to be regional. An S-mode principal component analysis was performed on the inter-station correlation matrix of the rainfall data for the period 1941 - 1984. The earlier years had too many missing data values and were therefore excluded from the analysis. Thirteen principal components which accounted for 81.3% of the total rainfall variance were extracted. Since the initial principal components did not exhibit any regional pattern and therefore uninterpretable, they were subjected to orthogonal (Varimax option) and oblique (Oblimin option) rotations to improve on the interpretation. The varimax rotation isolated three distinct, significant and interpretable principal components PCI, PC2, and PC3 which explained 42.2% of the total variance in the original data set. Owing to their geographical locations the first component is named the Southern Component, the second, the Northern Component and the third, the Middle-Belt Component. The PC loadings were plotted in the co-ordinate systems PCI - PC2, PCI - PC3, PC2 - PC3, and the distinct clusters of stations mapped. Seven homogeneous rainfall regional groups were identified, namely, the Southern Coastal Area covering stations like Lagos, Benin, Ondo, Kwale, Owerri and Port-Harcourt; Calabar which stood alone on account of the effects of relief; the Southern Upland which comprised OgbomoshOyOyo, Ilorin, Offa, Ibadan, Akure, Auchi, Nsukka and Enugu; the Middle-Belt which included Lafia, Yola, Ibi, Bida, and Kaduna South; Jos, which stood alone due to the influence of Jos Plateau; the North-West made up of Sokoto, Birnin Kebbi, and Yelwa and North-East which comprised Katsina, Kano, Hadejia, Potiskum, Maiduguri and Nguru.
Description
A Thesis submitted to the Postgraduate School, Ahmadu Bello University, Zaria, in partial fulfilment of the requirement for the Degree of MASTER OF SCIENCE (M.Sc),
Keywords
ANALYSIS,, CHARACTERIZATION,, RAINFALL,, NIGERIA.
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