Downscaling Rainfall in Benin: A Deltaic City of the Niger Delta Region, under two Emission Scenarios

Abstract

This study endeavored to downscale rainfall in Benin City so as to reveal what pathway would be more tolerable in the metropolis both now and in the future, putting the current effect of rainfall in the area in mind. Quasi-experimental research design was adopted and data for rainfall (1985-2015) was collected from the archive of the Nigerian meteorological agency (NIMET). While data of large scale predictors were collected from the HadCM3 data achieve. Calibration period was from 1985 to 2001, while validation was 2001 to 2015. Analysis of variance was used to trace if there was a significant difference in the temporal rainfall characteristics for A2 and B2 emission scenarios. However the study found that the predictors that explain rainfall patterns in the area were Shum, Rhum, R850 and R500; and during calibration it was found that rainfall significantly depended on these predictors at P<0.05. However, during validation, statistics show that the models performed considerably well in which case the modeled data related well with the observed data for all seasons of the year i.e. DJF season r-0.92 (r²-0.85; RMSE 0.31; RSD, 0.89) at P<0.05; MAM r-0.81 (r²-0.66; RMSE 0.41; RSD, 0.91) at P<0.05; JJA r-0.76 (r²-0.58; RMSE 0.31; RSD, 0.97) at P<0.05; SON r-0.82 (r²-0.67; RMSE 0.26; RSD, 0.82) at P<0.05. However there are some uncertainties in the data set for which caution must be taken while relying on the out puts of the model of the current study. As a result, the study recommends the use of clean technology, and a development of flood risk preparedness to deal with flood effects as a result increasing amounts of rainfall in the metropolis amongst others.