Comparison of Rainy Season Onset, Cessation and Duration for Ghana from RegCM4 and GMet Datasets

Thesocio-economic sector of West African countries is rain-fed agriculture driven.Information regarding the onset, cessation and duration of the rainy season isthus, very essential. In this paper, a comparison of the onset, cessation andduration of the rainy season has been carried out using simulated rainfall datafrom the fourth generation Regional Climate Model (RegCM4) and rain gaugemeasurements from Ghana Meteorological Agency (GMet), covering a period of 1998to 2012. Similar onset and cessation dates were seen in both the simulated andguage rainfall measurements for the various agro-ecological zones, resulting insimilar duration of the rainy season. The average duration of the rainy seasonwere less than 200 days for the savannah and coastal zones whereas the durationof the rainy season were beyond 200 days for the forest and transition zones.The bias of these comparisons was less than 30 days and the root mean squareerror (RMSE) values were less than 15 days for all stations, except Saltpond.The Pearson’s correlation (r) typically ranged between 0.4 and 0.8. However,negative correlations were observed for Tamale in the savannah zone, and theentire coastal zone. These findings are indications that RegCM4 has thepotential to clearly simulate the movement of the rain belt, and thus, couldfairly determine the onset, cessation and duration of the rainy season. Thefindings have significant contributions to effective water resource managementand food security in Ghana, as the thriving of these sectors depend on thedynamics of the rainfall seasons.