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CR 28:109-122 (2005)  -  doi:10.3354/cr028109

Validation of a coupled GCM and projection of summer rainfall change over South Africa, using a statistical downscaling method

Yan Zhao1,2,*, Pierre Camberlin1, Yves Richard1

1Centre de recherches de climatologie, CNRS UMR 5080, Université de Bourgogne, Sciences Gabriel, 6 Bd Gabriel, 21000 Dijon, France
2Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG),Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing PO Box 9804, 100029 Beijing, China

ABSTRACT: In this study, the southern African climate response to increasing amounts of greenhouse gases is investigated, based on the dataset of a 150-yr climate change experiment following the IPCC Special Report on Emissions Scenarios marker scenario B2 (SRES-B2) performed with the coupled ARPEGE/OPA/GELATO general circulation model (GCM). The method of canonical correlation analysis (CCA) is adopted to validate the ability of the GCM to simulate the present-day climate over the southern African region and project the late-summer rainfall change over South Africa at the end of the 21st century. The model validation shows that the ARPEGE/OPA/GELATO GCM is able to capture the observed link between rainfall over South Africa and adjacent sea-level pressure (SLP), despite the existence of some systematic errors. The structure and variability of SLP are reproduced by the GCM in a realistic way. The major controlling mechanism of rainfall over South Africa can be identified in the GCM. The projection of rainfall indicates a drying trend during the 21st century over most parts of South Africa, in particular the central interior. Compared to present-day climatology, the overall late-summer rainfall will decrease by 8.2% by the end of 21st century as derived from GCM grid-point output, and by 16.1% from the downscaling model.

KEY WORDS: Climate change · Model evaluation · Statistical downscaling · Canonical correlation analysis · South Africa

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