ENSO signals in East African rainfall seasons

Abstract

The evolutions of ENSO modes in the seasonal rainfall patterns over East Africa are examined in this study. The study covers the period 1961–1990. Both rotated empirical orthogonal function (EOF) and simple correlation analyses were used to delineate a network of 136 stations over East Africa into homogeneous rainfall regions in order to derive rainfall indices. Time series generated from the delineated regions were later used in the rainfall/ENSO analyses. Such analyses involved the development of composite rainfall map patterns for El Niño and post‐ENSO (+1) years in order to investigate the associations between seasonal evolution of El Niño–Southern Oscillation (ENSO) 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 East Africa. The results showed unique seasonal evolution patterns in rainfall during the different phases of the ENSO cycles. East African rainfall performance characteristics were stratified to identify distinct rainfall anomaly patterns associated with ENSO and post‐ENSO (+1) years. These can be applied in conjunction with skilful long lead (up to 12 months) ENSO prediction to provide guidance on likely patterns of seasonal rainfall anomalies over the region. Such information can be crucial for early warning of socio‐economic disasters associated with extreme rainfall anomalies over East Africa. Copyright © 2000 Royal Meteorological Society

Climate Characteristics over Southern Highlands Tanzania

“…Moreover, tropical Indian Ocean is seen to be dominated by easterlies during this peak season as the result of warming of the SST in the west and cooling in the East Indian Ocean [28]. Taken together with this, the extreme continental southward location of ITCZ between Tanzania and central Mozambique during December and February [3,4,6,7], suggests a substantial rainfall over southern Tanzania during this period.…”

“…Nevertheless, rainfall variability over the East Africa with relation to regional and remote atmospheric and oceanographic parameters has been studied by many researchers (e.g. [3][4][5][6][7][8][9][10][11]). …”

“…[7,14]) have tried to delineate homogeneous rainfall region over East Africa and Tanzania in particular. Basalirwa et al [14] performed principal component analysis and delineate Tanzania into 15 homogeneous rainfall regions based on the network of 150 widely distributed rainfall stations.…”

“…Basalirwa et al [14] performed principal component analysis and delineate Tanzania into 15 homogeneous rainfall regions based on the network of 150 widely distributed rainfall stations. Indeje et al [7] performed another principle component analysis and simple correlation analyses using a network of 136 rain-fall stations over East Africa. Their analyses yielded 8 homogeneous rainfall regions over East Africa, among them, 5 were found in Tanzania.…”

Investigation of the possible influence of Urbanization on Rainfall Variability over Nairobi City, Kenya

“…King'uyu et al, 2011;Indeje et al, 2000) found significant station to station homogeneity. King'uyu et al (2011) used mass curves to test maximum temperature and rainfall data homogeneity using RClimdex.…”