Quasi-periodic patterns in the East African rainfall records
Abstract
In this study East African rainfall records within the period 1922-80 were
subjected to spectral analysis in order to examine whether the
fluctuations in rainfall during 1922-80 exhibited any periodic or quasi-periodic
patterns. The characteristics of the rainfall auto-correlations at
the individual stations were also analyzed. The data used here included
monthly and annual rainfall records of about 100 stations distributed all
over East Africa. Fluctuations in the regionally averaged rainfall records
were also examined.
Results from spectral analysis indicated that a family of four spectral
peaks were common in many rainfall records. The period of these peaks
was centred generally around 2.2 to 2.8 years, 3.0 to 3.7 years, 4.8 to 6.0
years, and 10.0 to 12.5 years. Although all these spectral peaks appeared
in many rainfall series, the proportion of the total rainfall variance
explained by each varied significantly from region to region.
Results- from auto-correlation analysis indicated that lag one
auto-correlations were significantly different from zero at 16 stations for
the annual records. The nature of persistence at these 16 stations was
observed to be close to the linear markov type. "Red noise'" hypothesis
was used in testing the statistical significance of the spectral peaks
observed at these stations while the "white noise" hypothesis was
employed in the other cases.
Citation
Kenya Journal of Science and Technology (A) (1982) 3: 43 - 54Publisher
Department of Meteorology, University of Nairobi
Description
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