West African monsoon (WAM) jump and its implication for rain-fed agriculture in the transition and coastal savannah agro-ecological zones of Ghana

Abstract

West African rainfall variability plays an essential role in the economies of West African countries it has a major influence on industrial and agricultural production, which is largely, weather dependent. This plays an important role in food security and water availability. This work focuses on the West African Monsoon (WAM) jump and its implication for rain-fed agriculture in the Transition and Coastal Savannah agro-ecological zones of Ghana. In this study, the seasonal rainfall variability over West Africa is investigated using GPCP satellite data. Again, rainfall data from Wenchi in the Transition zone and Saltpond in the Coastal Savannah agro-ecological zone from 1990 to 2008 were acquired from the Ghana Meteorological (GMet) Agency for the study. The seasonal rainfall variability over these synoptic stations was studied in two climatological periods from 1990-1998 and 2000-2008 hereafter called CP1 and CP2 respectively. The agricultural implication is also checked. The results helped establish the rainfall regimes between these two climatological periods with CP1 being wet and CP2 being dry across West Africa. The rainfall peaks was found to have been shifting to later dates in CP2. Rainfall intensity in Wenchi was found to have a little reduction in the later part of the year across both CP1 and CP2 with the effect much felt in CP2. Saltpond also suffered a significant decrease in rainfall intensity over the minor season. Length of rainfall in high maize yield years selected randomly was found to be higher than that of randomly selected low maize yield years in Wenchi whereas in Saltpond, rainfall length was higher in low yield years than the that of the high yield years.