Spatio-Temporal Modelling of Dust-Induced Rainfall Anomalies in Northern Ghana

Rainfall variability in Northern Ghana has increasingly become a topic of concern, especially in light of the current global climate change crisis Due to its savannah ecosystem, Northern Ghana is known for and prone to extreme climatic conditions. During the dry season, dust from the Bodélé Depression in the Chad Basin is carried by Harmattan winds throughout the region, where it interacts with other environmental variables in the atmosphere, including precipitation. The effects of dust on precipitation are generally categorised as direct, semi-direct and indirect effects. In the past decades, rainfall anomalies due to several factors have affected livelihoods in the region. In this context, satellite (CHIRPS, MODIS) and reanalysis (ERA5) datasets were utilised. This study thus used Empirical Orthogonal Functions (EOF) and Singular Value Decomposition (SVD) analysis to investigate the spatio-temporal trends and patterns of dust and rainfall during the transition period from the dry to wet season (March, April and May) from 2004 to 2024 in Northern Ghana and found that the first coupled mode which explained majority of the variability demonstrated a pattern of increased dust aerosol and reduced precipitation in most of the region. In addition, this statistical relationship is supported by physical data obtained from wind/humidity profiles and cloud microphysics analyses. Because the region is largely dependent on rainfed agriculture, a climate trend analysis of the Normalised Difference Vegetation Index (NDVI) was also performed to assess the impact these rainfall anomalies have had on vegetation cover by correlating annual rainfall and mean NDVI during the study period in the region. The Mann–Kendall and Sen’s Slope Tests were then used to evaluate the vegetation greenness change in the study area and its magnitude during the 21-year period.