Regional climate model simulation of projected 21st century climate change over an all-Africa domain: Comparison analysis of nested and driving model results

• Published in: Journal of Geophysical Research 2011-08, Vol.116 (D15), p.n/a, Article D15111
• Main Authors: Mariotti, L., Coppola, E., Sylla, M. B., Giorgi, F., Piani, C.
• Format: Article
• Language: English
• Subjects: Atmospheric sciences; Climate change; Climate models; driving global climate model; Earth; El Nino; Geophysics; land surface processes; regional model; Regions; Soil moisture; transient climate change; Tropical environments
• ISSN: 0148-0227; 2169-897X; 2156-2202; 2169-8996
• DOI: 10.1029/2010JD015068

We analyze a transient climate change simulation for the 21st century (1980–2100) over a large all‐Africa domain carried out with the RegCM3 regional model driven by the ECHAM5 global model. We focus the analysis on a comparison between the driving and nested model runs. For present climate, the two models show temperature and precipitation biases of similar magnitude but different spatial patterns. In particular the bias patterns in the regional model driven by ECHAM5 are more similar to those of a regional simulation driven by ERA Interim reanalysis fields than to the bias patterns in the present climate simulation by ECHAM5 itself. In the transient simulation, while the temperature changes are strongly driven by the global model, the precipitation change patterns are more different between the global and regional models, particularly over the West Africa and Sahel regions. A targeted analysis suggests that this is due to the different simulation by the two models of the local response to El Niño–Southern Oscillation forcing and of local soil moisture/precipitation feedbacks. Our results thus indicate that local processes and internal model physics and characteristics are important elements in determining the precipitation change signal simulated by the nested regional model in this large domain experiment, especially over equatorial and tropical regions. This adds an element of uncertainty that needs to be address through the use of ensembles of regional model experiments as planned in the Coordinated Regional Climate Downscaling Experiment (CORDEX) project. Key Points For present climate the models show rainfall biases with different spatial patterns The precipitation change patterns are more different over West Africa and Sahel Differences due to local response to ENSO forcing and soil moisture/precipitation