Abstract
Characterizing seasonal rainfall and identifying its association with the climate drivers are important to produce reliable seasonal climate forecasts of a given area. This study examined the rainfall variability and its relationships with SST, SLP and sunspot indices by statistical methods over Western Oromia. The regional is characterized by monomodal pattern of 60% seasonal rainfall contribution in Kiremt season. High temporal anomaly rainfall but no extremes were observed from 1981-2017. An insignificant decreasing Kiremt and Belg but, an increasing Bega trend was observed. ENSO and PDO/ DMI and AMO showed negative/ positive correlation with kiremt rainfall. ENSO, DMI and AMO showed positive correlation for belg rainfall whereas, PDO showed associated negatively for the most parts of the region. PSI to kiremt/Belg rainfall correlation showed significant positive/Negative spatial association over the western part (West Wolega and Illubabor) / the East part (Jimma & East wollega) of the region. The results showed that there is decreasing trends in rainfall anomalies for main rainy seasons of region and good correlations these various indices. Therefore, it is suggested that seasonal climate predictions may consider these large-scale determinants oscillation indices like AMO and PDO in predicting climatic events. Â
Highlights
Climate events that observed in the most parts of Africa are increasing and consistent with expectation from different forces (Friederike et al, 2018)
Several climate studies over East Africa examined the link of Belg and Kiremt rainfall with phase of El Niño Southern Oscillation(ENSO) (Diro, 2019; Daniel, 2019; and segele,2009), Indian Ocean Dipole(IOD) (Shanko,1998), and North Atlantic Oscillation(NAO) as major drivers of regional intraseasonal rainfall variability
The Belg rainfall is negatively correlated with NAO over much of the eastern southern Ethiopia (Endalkachew, 2015)
Summary
Climate events that observed in the most parts of Africa are increasing and consistent with expectation from different forces (Friederike et al, 2018). Several climate studies over East Africa examined the link of Belg and Kiremt rainfall with phase of El Niño Southern Oscillation(ENSO) (Diro, 2019; Daniel, 2019; and segele,2009), Indian Ocean Dipole(IOD) (Shanko,1998), and North Atlantic Oscillation(NAO) as major drivers of regional intraseasonal rainfall variability. The complexity in Ethiopian rainfall character that change markedly in amount over short distances is the results of the over all of various factors ranging from large scale to more regional elements(Levizzani,20018; Degefu, 2017; Shanko,1998; Diro, 2011 and Gissila, 2004) This rainfall variability induces significant social, economic and environmental impacts and considerable challenge in the world mainly in developing countries (Bezu, 2020). The find may contribute for understanding the rainfall climate; provide valuable information in providing reliable weather and climate forecasts for users that minimize the impacts of climate events in the region
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