SPACE-TIME VARIABILITY OF RAINFALL IN APRIL AND OCTOBER NOVEMBER OVER EAST-AFRICA DURING THE PERIOD 1932-1983

The space–time variability of precipitation over East Africa during the two rainy seasons (April and October–November) is investigated using a network of 56 stations for the period 1972–1983 and 32 stations for the period 1932–1983. The analysis relies on a model of two‐mode variance with rotation, which determines homogeneous groups of stations having a common time evolution. During April, three components represent a large part of the variance with their cores (i) near the Zanzibar channel, (ii) the Kenyan‐Tanzanian highlands and eastern Lake Victoria, and (iii) the southern part of the Tanzanian highlands. During the October–November rainy season, rainfall is more homogeneously distributed. The first component takes account of 60 per cent of the variance and encompasses a large part of the domain, except southern inland Tanzanian stations and western and northern Ugandan stations. Spectral analysis of the time series associated with the space component reveals peaks around 5–6 years, which appears to be the major periodicity over East Africa. Copyright © 1990 John Wiley & Sons, Ltd