Precipitation Climatology in an Ensemble of CORDEX-Africa Regional Climate Simulations

TLDR

These simulations represent the first set of regional climate runs in the CORDEX‑Africa project. The study evaluates how well ten regional climate models and their ensemble mean reproduce African precipitation. All ten RCMs, operating at ~50 km resolution and driven by ERA‑Interim (1989–2008), are assessed against observations across seasonal, annual, and diurnal timescales. The models capture seasonal and annual precipitation patterns accurately, though individual biases exist; the multimodel mean generally outperforms single models and improves upon the boundary‑condition dataset, yet most models mis‑timed diurnal precipitation and the ensemble does not correct this, indicating the set is suitable for climate projections over Africa.

Abstract

Abstract An ensemble of regional climate simulations is analyzed to evaluate the ability of 10 regional climate models (RCMs) and their ensemble average to simulate precipitation over Africa. All RCMs use a similar domain and spatial resolution of ~50 km and are driven by the ECMWF Interim Re-Analysis (ERA-Interim) (1989–2008). They constitute the first set of simulations in the Coordinated Regional Downscaling Experiment in Africa (CORDEX-Africa) project. Simulated precipitation is evaluated at a range of time scales, including seasonal means, and annual and diurnal cycles, against a number of detailed observational datasets. All RCMs simulate the seasonal mean and annual cycle quite accurately, although individual models can exhibit significant biases in some subregions and seasons. The multimodel average generally outperforms any individual simulation, showing biases of similar magnitude to differences across a number of observational datasets. Moreover, many of the RCMs significantly improve the precipitation climate compared to that from their boundary condition dataset, that is, ERA-Interim. A common problem in the majority of the RCMs is that precipitation is triggered too early during the diurnal cycle, although a small subset of models does have a reasonable representation of the phase of the diurnal cycle. The systematic bias in the diurnal cycle is not improved when the ensemble mean is considered. Based on this performance analysis, it is assessed that the present set of RCMs can be used to provide useful information on climate projections over Africa.