Expected future changes in the African monsoon between 2030 and 2070 using some CMIP3 and CMIP5 models under a medium-low RCP scenario

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Expected future changes in the African monsoon between 2030 and 2070 using some CMIP3 and CMIP5 models under a medium-low RCP scenario

par Paul-Arthur Monerie, Bernard Fontaine et Pascal Roucou (CRC)

Accepté pour publication dans la revue Journal of Geophysical Research

The accuracy of African Monsoon (AM) simulations together with expected future changes are presented using eight available CMIP5/AR5 AOGCMs under the RCP4.5 emission scenario and eight CMIP3/AR4 AOGCMs under the A1b scenario, with a multimodel approach and the “one model one vote” concept. The results refer to the ‘present’ period (1960–1999) and to a ‘future horizon’ (2031–2070), and are discussed in terms of monsoon dynamics and climate change. Overall the new simulations seem more realistic. They exhibit more accurate rainfall patterns, although some biases reported in CMIP3 models remain. The future changes show an inverse tendency regarding rainfall amounts with less (more) rainfall expected over the western (central-eastern) Sahel. The deficits are associated with increasing air subsidence and the surplus with a more intense monsoon circulation. An African Rainfall Pattern Index (ARPI), based on standardized rainfall differences between these regions, is defined for capturing the rainfall contrast over the period from 1900 to 2100. This index increases suggesting that the contrasted rainfall anomaly pattern at Sahelian latitudes is expected to occur more frequently in the future.