Enso signals in East African rainfall seasons
View/ Open
Date
2000Author
Ogallo, Laban J.
Semazzi, Fredrick H.M.
Indeje, Matayo
Type
ArticleLanguage
enMetadata
Show full item recordAbstract
The evolutions of ENSO modes in the seasonal rainfall patterns over East Africa are examined in this study. The
udy covers the period 1961-1990. Both rotated empirical orthogonal function (EOF) and simple correlation
ialyses were used to delineate a network of 136stations over East Africa into homogeneous rainfall regions in order
I derive rainfall indices. Time series generated from the delineated regions were later used in the rainfall/ENSO
ialyses. Such analyses involved the development of composite rainfall map patterns for EI Nino and post-ENSO
+ 1) years in order to investigate the associations between seasonal evolution of EI Nino-Southern Oscillation
~NSO)signals and the space-time evolution of rainfall anomalies over the region.
Analyses based on both EOF and simple correlation techniques yielded eight homogeneous rainfall regions over
ast Africa. The results showed unique seasonal evolution patterns in rainfall during the different phases of the
NSO cycles. East African rainfall performance characteristics were stratified to identify distinct rainfall anomaly
atterns associated with ENSO and post-ENSO ( + 1) years. These can be applied in conjunction with skilful long
ad (up to 12 months) ENSO prediction to provide guidance on likely patterns of seasonal rainfall anomalies over
Ie region. Such information can be crucial for early warning of socio-economic disasters associated with extreme
iinfall anomalies over East Africa. Copyrighr'O 2000 Royal Meteorological Society.
Citation
I. J. Climatol. 20: 19-46 (2000)Publisher
Royal Meteorological Society Department of Meteorology, University of Nairobi, Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA