|dc.description.abstract||Accurate rainfall forecasts would greatly improve the quality and quantity of
agricultural products and other rain dependent activities, while allowing for the
amelioration and integration of the catastrophic socio-economic impacts of
extreme rainfall events. Such forecasts are as yet unavailable and although numerical
models could Improve contemporary forecasts, their potentials remain unexploited in
The objective of this study was to establish the ocean-atmosphere anomalies
which have been associated with some of the periods of surplus and deficient rainfall
over the whole of East Africa, with a view of understanding some of the responsible
Monthly rainfall data for 50 East African stations were used to select years of
extremely dry and wet rainfall events, using an empirically derived rainfall index. NOAA
Outgoing long wave radiation (OLR) data for 1974-1988 at 5° x 5° lat/longitudes and
Sea surface temperatures (SST) data for 1970-1984 at 2° x 2° from the UK
Meteorological office were then subjected to a number of statistical analyses including
Empirical Orthogonal Function Analysis (EOF). The December-February, March-May,
June-August and September-November seasons were each investigated independently
during the years of extreme rainfall anomalies.
The most distinct feature of the OLR anomalies was the opposite response
depicted between the west Indian Ocean and the eastern side extending into Indonesia.
During the wet years, enhanced cloudiness dominate East Africa and west Indian
Ocean, while clear conditions prevail over the east Indian Ocean and the Indonesian
region. The corresponding SST anomalies depict tendencies for warm (cold) SST
anomalies over west Indian Ocean to occur during the wet (dry) years. The east Atlantic
SST anomaly patterns were not very consistent with cold anomalies occurring in the wet
years of some seasons while warm anomalies occur in others.
In the dry year the OLR dipole between east and west Indian Ocean is reversed.
Results from peA indicated that, the first OLR eigen mode which is associated with the
Saharan anticyclone was strongly correlated with seasonal rainfall anomalies over
East Africa. Which IS reflective of the strong influence of the synoptic scale systems.
The study has shown that ocean-atmosphere anomalies over the Indian Ocean
significantly influence rainfall events in East Africa.||en