| dc.description.abstract | This study has used principal component analysis, composite analysis
and correlation analysis to establish the sea surface temperature modes that
could represent the combined influence of the Atlantic and Indian Oceans on
the seasonal rainfall over East Africa. The results from principal component
analysis indicated that sixteen, sixteen, fifteen, and fourteen modes, accounting
for about 93%, 94%, 93%, and 93% of the total seasonal sea surface temperature
variance, were significant for the December-February, March-May, June-
August and September-December periods, respectively. Most of the first four
modes represented sea surface temperature variability associated with the individual
oceans such as basin wide warming/cooling associated with El Niño/
Southern Oscillation, inter-hemispheric SST variability over the Atlantic Ocean,
and Indian Ocean Dipole. The decadal and inter-decadal variability were observed
with the time coefficients associated with the modes.
The results from correlation analysis indicated that the mode representing
Atlantic-Indian Ocean Dipole together with the associated gradient has significant
relationships with rainfall for March-May and September- December
periods. The gradient mode accounted for the highest rainfall variance with
September-December rainfall. The use of the gradient mode improved the values
of correlation compared to those observed with the sea surface temperatures
of the centres used to develop the mode indicating the ability of the gradient
modes to improve relationships with rainfall.
The results from composite analysis indicated that the gradient associated
with the mode delineated the March-May and September-December rainfall
associated with its opposite phases. The opposite phases of the mode were
associated with opposite patterns of seasonal rainfall and wind currents confirming
that the observed relationships are realistic.
These results have documented a mode together with the associated
gradient that can be used to represent the combined influence of the Indian and
Atlantic oceans on the rainfall over the region, and improve the monitoring and
prediction of seasonal rainfall over the region. However, more studies need to
be done to understand further the dynamics of this mode and its association
with rainfall over the region. | en |
