Climate of the Congo Basin

Abstract This chapter provides an overview of the current understanding of the key features of the Congo Basin’s climate. It presents the main features that characterize the dynamics of air masses, the hydrological cycle, and the spatial and temporal variability of precipitation. The lower tropospheric circulation is dominated by low-level westerlies, which transport moisture from the Atlantic Ocean inland and sustain deep convection and rainfall throughout the year. This moist air converges with dry easterly air along the Congo Air Boundary, marking the southern limit of convection. Mass convergence causes ascent and warming of moist air parcels, destabilizing the atmosphere and causing upward motion. This is balanced by a mid-tropospheric easterly flow, leading to a shallow east-west overturning circulation known as the Congo Basin cell. Although the cell does not regulate rainfall, it may play a role in rainfall distribution through the position of the rainfall maximum. Mesoscale convective systems (MCSs) are the principal rainfall producers, accounting for up to 80% of annual precipitation and contribute to exceptionally high lightning activity. The hydrological cycle is strongly modulated by evapotranspiration and rainfall recycling, with evidence that local vegetation contributes significantly to atmospheric moisture supply. Regional climate variability reflects complex teleconnections with Atlantic, Indian, and Pacific Ocean sea-surface temperature, though the strength and consistency of these links remain debated. A persistent challenge is the scarcity of reliable, long-term observational data, particularly rainfall and upper-air records, which undermines model validation and projection accuracy. Addressing these gaps is essential for improving climate prediction and informing sustainable management of this critical climate-regulating region.