Recorded presentation6A.2
Variability of the West African monsoon system in the new NCEP CFS model
Wassila M. Thiaw, NOAA/NWS/NCEP/CPC, Camp Springs, MD; and V. B. Kumar, K. C. Mo, and A. Vintzileos
The NCEP coupled forecast system (CFS), a fully coupled ocean-atmosphere model, is used to diagnose the predictability of the African climate on the seasonal to interannual time scale. Earlier results with CFS runs at T-62 indicated some difficulty in the model to reproduce the mean seasonal rainfall in the Sahel. The model also exhibited deficiency in depicting the magnitude of the interannual variability. This deficiency was attributed to model SST systematic errors and poor representation of soil moisture. Recently, EMC has made available several experimental hindcasts at various horizontal resolution and improved model physics of the CFS coupled with the new NCEP land model. We explore the new model's ability to reproduce the climate of West Africa. Preliminary results show an improvement in the representation of the West African summer precipitation and in depicting the interannual variability. The areas of maximum precipitation are well depicted and their magnitudes quite comparable to observations. Further, rainfall extends farther north in the Sahel than in the earlier CFS T62 run. There is also an improvement in the representation of the precipitation interannual variability. However, a slight overestimation of precipitation in the Gulf of Guinea region and the areas south of 15N is evident. The modes of variability that modulate key dynamic features of the West African monsoon system are investigated and the causes for model errors discussed. Finally, the potential use of CFS to improve seasonal rainfall predictions is discussed. Recorded presentation
Session 6A, African Climate: VI. Modeling Studies
Tuesday, 22 January 2008, 11:00 AM-12:00 PM, 215-216
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