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Communication incl. Poster: BibTeX citation key:  Patricola
Patricola, C. M. & Cook, K. H. 2009. West African climate at the end of the 21st Century: An integrated application of regional and global climate models. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-10-09 09:12:27    Last Edited by: roussot 2009-10-16 16:36:59
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Categories: Weather to Climatic modelling and forecasting
Keywords: Modelling
Creators: Cook, Patricola
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Abstract
GCM precipitation projections for northern Africa reported in the most recent IPCC report are inconsistent due, in part, to the GCMs’ inability to capture climate processes correctly, deficiencies in physical parameterizations, different SST projections, treatment of the land surface, or resolution that is too coarse. Here a method for simulating future climate is developed and applied using ensemble regional modeling with output from AOGCMs to supply future SST and lateral boundary condition anomalies. The control simulation (1981-2000) validates well, and nine ensemble simulations representing 2081-2100 are produced.
Unlike the IPCC AOGCMs, the regional model ensemble members are largely consistent in their prediction of future rainfall anomalies over West Africa. In May, rainfall increases of 25 – 50% are simulated for West Africa, indicating an earlier start to the monsoon season in the future. In contrast, June and July rainfall rates are reduced by 50%, accompanied by significant increases in the high heat index values that are associated with the occurrence of heat stroke. The enhanced drying is relieved in late summer and fall by precipitation rates that are about 50 – 100% greater than today’s climate, but the distribution of rainfall rates shifts to higher values, indicating a possibility for more extreme rainfall events and flooding.
Confidence in the results is bolstered by the good agreement among the ensemble members and by studying the physical processes that cause climate to change using simulations in which the future forcing factors are applied individually and other idealized simulations. For example, CO2 increases alone enhance the monsoon and produce wetter conditions throughout the summer, while the simulated mid-summer drying is related to a slowing of the large-scale tropical circulation and warming SSTs.
Last Edited by: roussot