(Pohl andCamberlin 2011) indicated that both inter-annual variability and intraseasonal variabilityover equatorial East Africa are strongly controlled by zonal wind shear (the difference between 850 hPa and 150 hPa winds)over the central equatorial Indian Ocean. They concluded that it holds for allseasons except boreal summer when thewinds at both levels are relatively constant. They also found out that theshear is more closely correlated with ENSO than with the IOZM in all seasons exceptboreal summer. (Gong et al., 2016) analyzed the inter-annual linkage betweenthe boreal winter Arctic Oscillation (AO) and East African early short rains.
When the Indian Ocean Dipole and El Nino/ Southern Oscillation variance wereexcluded by linear regression, the boreal winter AO index was significantly correlatedwith the October East African precipitation, whereby the upper ocean heatcontent likely acts as a medium that links the AO and East Africanprecipitation. It was also concluded that there was a significant inter-annualrelationship between East African early short rains and boreal winter ArcticOscillation which induces anomalous wind stress curl in the tropical Indian Ocean and generates oceanicRossby waves, whereby the d own welling Rossby waves lead to anomalous upperocean heat content which enhance precipitation over East Africa in October.In general,precipitation events during the long rains (MAM) season tends to be heavier andlonger in duration, with less inter-annual variability, and are more likelyassociated with local factors. In contrast, precipitation events during theshort rains (SON) season are less intense with shorter duration and strongerintra-seasonal and inter-annual variability that mirrors large-scale phenomenasuch as ElNino-Southern Oscillation (ENSO) and the varying intensity of thezonal circulation cell along the equatorial Indian Ocean (Chan et al.,2008) and citations there in.In this studythe main objective is to investigate the variationof precipitation in East Africa during the SON season and the major effectsfrom the North Atlantic Oscillation, which has not been undertaken before savefor (Shilenje et al.
, 2015) with a study to investigate the relationshipbetween the North Atlantic Ocean Oscillation Index (NAOI) and October –December(OND) rainfall variability over Kenya, and found out that the correlationbetween NAOI and OND rainfall over Kenya is generally low and highly variablein space ranging from negative to positive correlation. The results show that avery small area in the western part of Kenya exhibits a significant correlationbetween NAOI and OND rainfall.