Decadal Rainfall variability modes in Observed Rainfall records over East Africa and their relations to historical Sea Surface temperature Changes
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Date
2012-07-14Author
Omondi P., Awange J.L, Ogallo L.A, Okoola R.A
Type
ArticleLanguage
enMetadata
Show full item recordAbstract
Detailed knowledge about the long-term interface of climate and rainfall variability is essential for man-
aging agricultural activities in Eastern African countries. To this end, the space–time patterns of decadal
rainfall variability modes over East Africa and their predictability potentials using Sea Surface Tempera-
ture (SST) are investigated. The analysis includes observed rainfall data from 1920 to 2004 and global
SSTs for the period 1950–2004. Simple correlation, trend and cyclical analyses, Principal Component
Analysis (PCA) with VARIMAX rotation and Canonical Correlation Analysis (CCA) are employed. The
results show decadal signals in filtered observed rainfall record with 10 years period during March–
May (MAM) and October–December (OND) seasons. During June–August (JJA), however, cycles with
20 years period are common. Too much/little rainfall received in one or two years determines the general
trend of the decadal mean rainfall. CCA results for MAM showed significant positive correlations between
the VARIMAX-PCA of SST and the canonical component time series over the central equatorial Indian
Ocean. Positive loadings were spread over the coastal and Lake Victoria regions while negative loading
over the rest of the region with significant canonical correlation skills. For the JJA seasons, Atlantic SSTs
had negative loadings centred on the tropical western Atlantic Ocean associated with the wet/dry
regimes over western/eastern sectors. The highest canonical correlation skill between OND rainfall and
the Pacific SSTs showed that El Niño/La Niña phases are associated with wet/dry decades over the region
Publisher
Department of Meteorology