Dynamic analysis of the West African Monsoon and its variability over Ghana

Abstract

In this study, the International Center for Theoretical Physics’ Regiona l Climate Model Version 4 (RegCM4) is used over the period 1998-2010, to study the dynamics of rainfall over West Africa. The study also attempts to understand the West African Monsoon (WAM) circulation and its characteristics. Global Precipitation Climatology Project precipitation (GPCP), Tropical Rainfa ll Measuring Mission (TRMM), global atmospheric reanalysis (ERA-Inter im, ERAINT), RegCM4 winds and National Centers for Environmental Prediction (NCEP) reanalysis were used to aid in the understanding of the WAM circulat ion dynamics. The main WAM circulation features and the general pattern of rainfa ll in the model simulation compare well with observations. The model simulates the mean rainfall at the peak of the West African summer rainy season (June-July- August), and it captures well the rainbelt associated with the ITCZ. Examination of the intraseasonal variability of rainfall shows that the model captures the three distinct phases of the West African monsoon circulation: onset, intensification and cessation phases. The simulation, for the monthly variability, well depicts the bimodal and unimodal nature of rainfall over southern and northern Ghana respectively. The association between Sea Surface Temperatures (SSTs) and rainfall showed a high positive correlation in most part of the Guinean Coast over the June-July-August (JJA) rainfall season. This depict that a rise in temperatures over the ocean is associated with high rainfall over the coast of West Africa including Ghana.