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Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first model intercomparison experiment |
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| Authors: | Yongkang Xue Fernando De Sales W K-M Lau Aaron Boone Jinming Feng Paul Dirmeyer Zhichang Guo Kyu-Myong Kim Akio Kitoh Vadlamani Kumar Isabelle Poccard-Leclercq Natalie Mahowald Wilfran Moufouma-Okia Phillip Pegion David P Rowell Jae Schemm Siegfried D Schubert Andrea Sealy Wassila M Thiaw Augustin Vintzileos Steven F Williams Man-Li C Wu |
| Institution: | 1. University of California, Los Angeles, CA, USA 2. Goddard Space Flight Center, NASA, Greenbelt, MD, USA 3. Centre National de Recherches Météorologiques, Météo-France Toulouse, Toulouse, France 4. Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China 5. Center for Ocean-Land-Atmosphere Interactions, Calverton, MD, USA 6. University of Maryland Baltimore County, Baltimore, MD, USA 7. Meteorological Research Institute, Tsukuba, Japan 8. National Center for Environmental Prediction, Camp Springs, MD, USA 9. Wyle Information Systems, Gaithersburg, MD, USA 10. Centre de Recherches de Climatologie UMR5210 CNRS, Université de Bourgogne, Dijon, France 11. Cornell University, Ithaca, NY, USA 12. Met Office Hadley Centre, Exeter, UK 13. The Caribbean Institute for Meteorology and Hydrology, St. James, Barbados 14. Science Applications International Corporation, Camp Springs, MD, USA 15. National Center for Atmospheric Research, Boulder, CO, USA |
| Abstract: | This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models’ (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among models in simulating spatial correlation, intensity, and variance of precipitation compared with observations. Furthermore, the majority of models fail to produce proper intensities of the African Easterly Jet (AEJ) and the tropical easterly jet. AMMA Land Surface Model Intercomparison Project (ALMIP) data are used to analyze the association between simulated surface processes and the WAM and to investigate the WAM mechanism. It has been identified that the spatial distributions of surface sensible heat flux, surface temperature, and moisture convergence are closely associated with the simulated spatial distribution of precipitation; while surface latent heat flux is closely associated with the AEJ and contributes to divergence in AEJ simulation. Common empirical orthogonal functions (CEOF) analysis is applied to characterize the WAM precipitation evolution and has identified a major WAM precipitation mode and two temperature modes (Sahara mode and Sahel mode). Results indicate that the WAMME models produce reasonable temporal evolutions of major CEOF modes but have deficiencies/uncertainties in producing variances explained by major modes. Furthermore, the CEOF analysis shows that WAM precipitation evolution is closely related to the enhanced Sahara mode and the weakened Sahel mode, supporting the evidence revealed in the analysis using ALMIP data. An analysis of variability of CEOF modes suggests that the Sahara mode leads the WAM evolution, and divergence in simulating this mode contributes to discrepancies in the precipitation simulation. |
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