Secular variation in South African rainfall
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Date
2015-03-10
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Abstract
Annual rainfall totals over South Africa during
the period 1910 - 1972, and where availability of data
permitted for the period 1880 - 197J, are examined for
evidence of secular variation. It is shown that no
evidence exists to support the view that the sub-continent
is undergoing progressive desiccation. With the aid of a
linear model station records, grouped using principal
component ana? vsis, are shown in some cases to possess
trend on a micro-scale.
Strong evidence is provided to support the hypothesis
that rainfall is oscillatory in nature. Oscillations in
the ranges 16-20, 10-12, and 2 - 3 years are shown by
different methods to be spatially dependent. A 3 - 4
year oscillation is ubiquitous.
The plausibility of using stochastic models to forecast
annual rainfall totals is investigated and tentative
forecasts made regarding the general pattern of rainfall
behaviour over some regions of South Africa.