Abstract
AbstractAs one of three global hot spots of tropical convection, potential future changes to the Congo Basin climate system will have regional and tropics‐wide implications. However, the latest generation of climate models from the Coupled Model Intercomparison Project 5 disagree on the sign and magnitude of future change and diverge in their estimation of the historical rainfall climatology. This study assesses the plausibility of different signals of future rainfall change by examining the processes relating to rainfall projections in samples of historically wet or dry models during the September–November rainy season. In the west Congo Basin, there are no significant differences in rainfall change projections in models that are historically wet or dry. Both composites feature wetting in the north (up to 1.8 mm/day) and drying in the south, associated with enhanced tropical Atlantic sea surface temperatures, increased evaporation, and enhanced low‐level moisture flux into the basin. In the east Congo Basin, there is greater evidence that differences in model historical climatologies has an influence on the magnitude of future rainfall change. Historically wet models project significant wetting in the northeast (1.19 mm/day) associated with a weakened northern component of the African Easterly Jet (AEJ) and enhanced moisture convergence. Dry models do not capture the structure of the AEJs in the historical period, and so changes to the AEJs under warming do not produce the same wetting pattern. The analysis therefore casts doubt on the plausibility of the driest rainfall change signals in the east Congo Basin.
Highlights
The continent of Africa is vulnerable to climate change (Niang et al, 2014)
We extend the process‐based analysis to future rainfall changes within the same groups of models in order to establish whether categorizing models by their historical climatology results in different future rainfall signals
Rainfall across models concurs, returning an r value of 0.67 (p = 0.003) for the east Congo Basin. These results suggest that categorizing the models on their historical climatology in the two sets of models has an impact on both the pattern and magnitude of the future rainfall change signal in this region
Summary
The continent of Africa is vulnerable to climate change (Niang et al, 2014). Research into climate change in the continent has focused predominantly on the subregions of West Africa and the Sahel (e.g., Biasutti & Sobel, 2009; Cook & Vizy, 2006; Hoerling et al, 2006; James et al, 2015; Vizy et al, 2013), East Africa (e.g., Hirons & Turner, 2018; Kent et al, 2015; Shongwe et al, 2011), and southern Africa (e.g., Kay & Washington, 2008; Lazenby et al, 2018; Shongwe et al, 2009) and has led to an improved understanding of the climate systems and projections in these areas Despite this progress, there remains a dearth of scientific research into the historical and future climate in the Congo Basin (James & Washington, 2013; Washington et al, 2006), the convective core of the continent and one of the three wettest places on Earth, alongside the Amazon Basin and Maritime Continent (Webster, 1983). It is imperative that uncertainty in the climate response in this region is reduced, so that decision makers have the most robust evidence available for policy decisions
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