Understanding the Influence of the Dynamics of Moisture Convergence on Rainfall in West Africa

Abstract

The main goal of this study is to thoroughly examine the behavior of vertically integrated moisture flux convergence (MFC) and moisture flux across West Africa. We aim to gain valuable insights into how these complex atmospheric processes relate to rainfall patterns. The study covers two significant time spans: 1981 to 2005, allowing us to analyze historical trends, and 2006 to 2100, providing a look ahead in the context of potential climate shifts. To conduct this study, we have heavily relied on robust datasets. The Climate Research Unit observational datasets and ERA-5 data from 1981 to 2005 have formed a strong foundation for our analysis. Additionally, we have used model outputs from the Coordinated Regional Down-scaling Experiment (CORDEX)-Africa to enhance the comprehensiveness of our research and accurately depict climatic conditions. To calculate moisture flux convergence (MFC), we carefully processed specific humidity, rainfall, and evaporation data extracted from the selected datasets. Similarly, we integrated specific humidity and horizontal wind data to compute moisture flux. These calculations, forming the core of our study, have revealed a noticeable difference in impact between MFC and wind convergence. Specifically, we computed characteristic impact values of 2.53mm/day and 1.6mm/day for MFC and wind convergence, respectively. One of the key findings of this research highlights the predominant influence of MFC on precipitation. This is supported by a strong positive correlation of 0.8315 observed between MFC and rainfall across the expansive West African region (WA), emphasizing the significant role of considering moisture flux dynamics in understanding and predicting rainfall patterns. Furthermore, our analysis involved computing the Rainfall Anomaly Index. This computation provided valuable insights into the changing pattern of drought occurrences. Notably, we observed a decline in drought incidence during the mid-21st century, followed by an increase towards the end of the century. This cyclic pattern suggests an increased likelihood of the region experiencing drier conditions as we progress further into the century.