资源环境科技发展态势分析平台

This study focuses on the relationship in global climate models between three features: the Saharan Heat Low (SHL), Sahel precipitation, and the Atlantic Intertropical Convergence Zone (ITCZ). Previous work showed that both coupled (CMIP) and uncoupled (AMIP) ocean/atmosphere models that place the SHL farther to the north are associated with increased precipitation across the Sahel. Further, the northward SHL placement is also associated with a northward shift in the Atlantic ITCZ in coupled CMIP models, but an eastward shift in uncoupled AMIP models. We perform three experiments with the Community Earth System Model to better understand relationships between these features. We find that when a northward-shifted Atlantic ITCZ is locally forced, there is no coherent response in the SHL and Sahel precipitation. However, when a northward-shifted Atlantic ITCZ is forced by altering the cross equatorial energy transport, the SHL shifts northward and Sahel precipitation increases, consistent with model biases. Finally, when the SHL strength is forced directly, there is a weak but robust increase in Sahel precipitation and a northward shift in the Atlantic ITCZ. The results of these experiments emphasize the important role of global scale energy biases on the simulation of West African climate, and show a possible feedback from West African climate onto the Atlantic ITCZ.