On the intra‐annual variation in rainfall over the sub‐continent of southern Africa

The variation in intra‐annual variance in rainfall over Southern Africa is examined for evidence to support the contention that it has undergone a systematic upward change over the period 1921‐1974. A principal components analysis on the data shows that the time series of intra‐annual variances may be represented by four components. Although each of the four principal component time series possesses an oscillation in the region of the biennial wave, there is little evidence to suggest that the within‐year variation in rainfall is undergoing any type of upward trend.