Modelling of Extreme Rainfall Patterns in Accra

Abstract

Concerns about climate change and its possible impacts on human activities have increased the ‎awareness that climatic conditions are dynamic. West Africa, of which Ghana is part is one of the ‎areas in the world that had experienced major climatic anomalies in the past century. The purpose ‎of this research is to model rainfall data using block maxima approach of extreme value theorem. ‎Monthly rainfall data covering the period 1960 – 2022 were obtained from the Ghana ‎Meteorological Agency, Accra Airport substation. Statistical properties of the data indicated data ‎was stationary, however it was not normally distributed. Time series analysis of the data indicated ‎consistent increase in rainfall values with both downward and upward spikes indicating ‎fluctuations in the rainfall values. The Generalized Extreme value distribution was used to fit the ‎model of rainfall values. The rainfall values were fitted using the Generalized Extreme value ‎distribution. The Fréchet distribution was found to be the most appropriate model for the monthly ‎rainfall data. Additionally, it was discovered that the amplitude of the extreme values grows with ‎return periods, with higher return levels predicted to become more uncommon but severe over ‎time‎.