The West African Monsoon Modeling and Evaluation project (WAMME) and its First Model Intercomparison Experiment

This paper presents the scientific challenge in West African monsoon (WAM) simulation and discusses the West African Monsoon Modeling and Evaluation project (WAMME) initiative and its approaches to improve WAM simulations. Major scientific highlights from the first WAMME model comparison are the focus of the paper. Based on the first WAMME experiment, the WAMME models' performance is evaluated with precipitation being the major focus. The analyses indicate that the models with specified SST generally have reasonable simulations of the mean spatial distribution of WAM precipitation but largely fail to produce proper daily precipitation frequency distributions. WAMME multi-model ensembles, however, produce excellent WAM precipitation spatial distribution, intensity, and temporal evolution, better than Reanalysis. In addition, the WAMME is the first project consisting of the most state-of-the-art general circulation models (GCMs) and regional climate models (RCMs) to collectively investigate the WAM/external forcing feedbacks. Cases based on the first WAMME experiment are presented to demonstrate scientific challenges for further investigation of WAM, SST, land, and aerosol interactions. The analyses in this article provide a quantitative assessment on model uncertainty, identify main issues in WAM modeling, and provide a good starting point as benchmarks for future studies.