Robust increase in extreme future precipitation in the Lake Victoria Basin based on km-scale regional climate projections

Abstract

Long multi-decadal transient convection-permitting climate simulations are crucial for reliable regional climate projections. However, the large computational resources required are often not available, particularly in the context of African climate change studies. This poses challenges for regions like the Lake Victoria basin, where extreme weather events, such as thunderstorms and associated wind gusts, result in high waves and flash floods with devastating impacts. Here, we configure a mini-ensemble of convection-permitting pseudo-global warming (PGW) regional climate simulations at 2.8 km for the Lake Victoria basin, providing a computationally efficient approach that allows us to assess model uncertainties related to changes in large-scale dynamics in the driving GCMs and identify robust climate change signals across the members. Our results reveal that, while extreme precipitation scaling is robust among the members (~5%/K), primarily driven by thermodynamic controls, the mean precipitation response is sensitive to uncertainties in large-scale dynamics, resulting in significant ensemble spread. Our projections indicate consistent drying over Lake Victoria during 18-24h UTC (21-03h local time) across the three ensemble members (up to −36% in the simulation with the strongest reduction in easterly trade winds), and a consistent shift from low and intermediate precipitation intensities to high values. Overall, despite uncertainties in large-scale dynamics, our ensemble projections provide critical insights for future climate resilience planning in the Lake Victoria basin.