Thursday, 13 February 2003: 3:45 PM
Evaluating the A1 scenario in the CCSM for West Africa: 20th and 21st century climates
The Community Climate System Model (CCSM) version 1 is evaluated over West Africa's wet season (JJAS) for the 1980s and 2080s. Our emphasis is on evaluating features associated with rain processes in West Africa. These features include: The surface meridional temperature gradient, the African Easterly Jet (AEJ), the Tropical Easterly Jet (TEJ) and African Easterly Waves (AEWs). When compared to the NCEP reanalysis, the CCSM does fairly good at capturing the AEJ and meridional surface temperature gradient but the TEJ is too weak over West Africa. The AEWs are also captured in the model, but the period of the waves are somewhat longer than suggested by the NCEP reanalysis. By the 21st century, temperatures are significantly warmer over much of West Africa with the largest warming occurring over the Sahara Desert. This temperature change leads to a poleward migration where the largest meridional temperature gradient is typically found, a slight poleward shift in the AEJ and an increase in rain over the Sahel region when compared to the late 20th century. Spectral analysis of the meridional winds suggests that the amplitude of the waves will decrease under the A1 scenario. Moreover, we have found that the CCSM can serve as boundary conditions for regional climate models studies in West Africa based.