An Investigation of Interannual Rainfall Variability in Africa

Open Access
Publisher Website
Google Scholar
Abstract
Interannual variations in African rainfall are examined using rotated principal component analysis (PCA) applied to anomalies from the annual mean as well as seasonal anomalies. The rotated PCA loading patterns suggest several “preferred” continental-scale rainfall anomaly patterns. The dominant features of year-to-year variations in African rainfall appear to be the high spatial coherence of rainfall anomalies over large portions of the continent. In addition, several dipole regions, that is, adjacent regions which tend to experience rainfall anomalies of opposite sign, are found and discussed. One dipole region, the sub-Saharan region, appears to have a relationship with a characteristic Atlantic sea surface temperature anomaly pattern during boreal summer. During austral summer, the tendency for a large-scale dipole pattern in southeast Africa is apparent, as is an association of this pattern with the warm and cold phases of the El Niñ/Southern Oscillation (ENSO) phenomenon. Normalized rainfal... Abstract Interannual variations in African rainfall are examined using rotated principal component analysis (PCA) applied to anomalies from the annual mean as well as seasonal anomalies. The rotated PCA loading patterns suggest several “preferred” continental-scale rainfall anomaly patterns. The dominant features of year-to-year variations in African rainfall appear to be the high spatial coherence of rainfall anomalies over large portions of the continent. In addition, several dipole regions, that is, adjacent regions which tend to experience rainfall anomalies of opposite sign, are found and discussed. One dipole region, the sub-Saharan region, appears to have a relationship with a characteristic Atlantic sea surface temperature anomaly pattern during boreal summer. During austral summer, the tendency for a large-scale dipole pattern in southeast Africa is apparent, as is an association of this pattern with the warm and cold phases of the El Niñ/Southern Oscillation (ENSO) phenomenon. Normalized rainfal...