ANALYSIS AND CHARACTERIZATION OF RAINFALL IN NIGERIA
ANALYSIS AND CHARACTERIZATION OF RAINFALL IN NIGERIA
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Date
1992-08
Authors
EKEMEZIE, ELIZABETH A.
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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.