Abstract:
A composite analysis is used to evaluate the teleconnections between the long term (June-
August) rainfall anomalies with east and west phases of quasi-biennial oscillation (QBO) in the
stratospheric zonal winds from 1979–2017. Applying the lower equatorial stratospheric zonal wind
index in JJA rainfall prediction is based on its tendency to persist for several months after the phase
change from easterly to westerly and vice versa. Below normal condition rainfall used to coin
drought. This study is important because, the Upper Blue Nile region is one of the most inviting
areas for different activities like agriculture and hydroelectric power; therefore, timely prediction of
June-August rainfall serves farmers and other concerned sectors. The aim of this analysis is to
establish the global signal quasi-biennial oscillation contribution alone at different time lags and its
association among Southern Oscillation Index (SOI) for estimation June-August rainfall of the Upper
Blue Nile. The rainfall used as predictand while quasi-biennial oscillation & SOI datasets are used as
predictors in regression model after testing collinearity of these two independent variables.
Performance of regression model and actual value is tested by using statistical techniques: Root
Mean Square Error, Mean Absolute Error and bias. The performance is seen reasonably high between
actual and estimated values show strong agreement.
