Modelling Rainfall Series in the Geo-Political Zones of Nigeria

Abstract

This paper applied time series analysis techniques to rainfall series in selected states of Nigeria geo-political zones. The preliminary analysis of the series showed that the mean annual rainfall for the selected states in North West, North central, North East, South West, South South and South East were 225.395, 269.938, 300.794, 323.634, 737.836 and 442.360 millimeters respectively. The correlogram of each series showed a positive autocorrelation and partial autocorrelation value at every seasonal, hence the inclusion of seasonal autoregressive in the model. On the basis that d=D=0, seasonal ARMA model was fitted to each series using AIC and SIC model selection criteria. The performance of the two criteria in selecting optimal model was found to be alike.

Keywords: Time series, correlogram, autocorrelation, seasonal, autoregressive