Kerry H. Cook
Department of Earth and Atmospheric Sciences
Cornell University
Ithaca NY 14853
The West African monsoon system exhibits unusual structure in both space and time that makes it a particular challenge for climate models. But this is one of the most important systems to properly simulate, since much of the population of northern Africa is vulnerable to climate variations and change through a strong dependence on local agriculture. This paper will provide an overview of the West African monsoon system, with the goal of identifying structures and processes within the system that a model needs to capture with some fidelity for a credible simulation of change and variability in this region. These include three important climatological jet features -the African easterly jet, the tropical easterly jet, and a low-level westerly jet that brings moisture onto the continent from the Atlantic - the southerly monsoon flow across the Guinean coast, and the thermal low/Saharan high complex. Important time-dependent features include the monsoon jump and monsoon breaks.
A comparison across a number of models, including atmosphere-only regional models and GCMs, coupled ocean/atmosphere regional models and GCMs (the AR4 models), and a regional ocean/atmosphere/vegetation model, will be used to understand to what extent we are able to produce a credible simulation of the West African monsoon system with current modeling tools, and what effort may produce improvements. Systematic errors will be reported and evaluated for both coupled and uncoupled models for the climatology of the summer precipitation and large scale circulation, and for the physics of the monsoon onset.
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