Radiative anomalies associated with extreme precipitation of November 2023 in equatorial Central Africa

Abstract

November 2023 was marked by abnormally heavy rainfall across equatorial Central Africa, causing considerable material damage and loss of life. The present study investigates the underlying mechanisms by examining the vertical advection of moisture and moist static energy (MSE) anomalies and the net energy flux components. We find that the vertical moisture and MSE advection components are mostly induced by vertical velocity anomalies (increase of up to 5 mm/day in moisture and 80 $W{m}^{-2}$ in MSE) rather than by specific humidity and MSE anomalies. Additionally, mean sea level pressure and 2 m temperature are significantly larger than climatology. The increase (decrease) in the mean net long (short) wave radiation of up to 30 $W{m}^{-2}$ at the top of the atmosphere and at the surface favored conditions of atmospheric instability. Analysis of the net energy flux indicates positive anomalies dominated by radiative anomalies (increase of up to 30 $W{m}^{-2}$), mainly along the Gulf of Guinea, while in the eastern Congo Basin, a decrease (up to −27 $W{m}^{-2}$) in the energy balance was observed during the formation of this extreme rainfall event. The results of this study highlight the importance of considering thermodynamic processes associated with radiative effects to accurately anticipate such events. Understanding these mechanisms is crucial for improving projections of climate extremes under the influence of global warming.