Journal of Climate, submitted 12/08.

The role of the Sahara low in Sahel rainfall variability and change in the CMIP3 models

Michela Biasutti
Lamont-Doherty Earth Observatory, Earth Institute at Columbia University, Palisades, NY

Adam H. Sobel
Department of Applied Physics and Applied Mathematics and Department of Earth and Environmental Sciences, Columbia University, New York, NY.

Suzana J. Camargo
Lamont-Doherty Earth Observatory, Earth Institute at Columbia University, Palisades, NY

Abstract

Projections for 21st century changes in Sahel precipitation dier greatly across models in the CMIP3 dataset, and cannot be explained solely in terms of discrepancies in the projected anomalies in global SST.

This study shows that an index describing the low-level circulation in the north Atlantic-African region, namely the strength of the low-level Saharan Low, can be used as a predictor for Sahel rainfall in all models and at all timescales.

An analysis of Sahel interannual variability provides evidence that variations in the Sahara Low can be a cause, not just a consequence, of variations in Sahel rainfall and suggests that a better understanding of the sources of model discrepancy in Sahel rainfall predictions might be gained from an analysis of the mechanisms influencing changes in the Sahara Low.