Changes in rainfall regime over Burkina Faso under the climate change conditions simulated by 5 regional climate models

Boubacar Ibrahim (1, 2) , Harouna Karambiri (1) , Jan Polcher (3) , Hamma Yacouba (1) , Pierre Ribstein (4)

1 2iE - Institut international d'ingénierie de l'eau et de l'environnement
2 West African Science Service Center on Climate Change and Adapted Land Use
3 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
4 METIS - Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols

Sahelian rainfall has recorded a high variability during the last century with a significant decrease (more than 20 %) in the annual rainfall amount since 1970. Using a linear regression model, the fluctuations of the annual rainfall from the observations over Burkina Faso during 1961–2009 period are described through the changes in the characteristics of the rainy season. The methodology is then applied to simulated rainfall data produced by five regional climate models under A1B scenario over two periods: 1971–2000 as reference period and 2021–2050 as projection period. As found with other climate models, the projected change in annual rainfall for West Africa is very uncertain. However, the present study shows that some features of the impact of climate change on rainfall regime in the region are robust. The number of the low rainfall events (0.1–5 mm/d) is projected to decrease by 3 % and the number of strong rainfall events ([50 mm/d) is expected to increase by 15 % on average. In addition, the rainy season onset is projected by all models to be delayed by one week on average and a consensus exists on the lengthening of the dry spells at about 20 %. Furthermore, the simulated relationship between changed annual rainfall amounts and the number of rain days or their intensity varies strongly from one model to another and some changes do not correspond to what is observed for the rainfall variability over the last 50 years.

Domaines: Climatologie

Boubacar Ibrahim, Harouna Karambiri, Jan Polcher, Hamma Yacouba, Pierre Ribstein. Changes in rainfall regime over Burkina Faso under the climate change conditions simulated by 5 regional climate models. Climate Dynamics, 2014, 42 (5-6), pp.1363-1381. ⟨10.1007/s00382-013-1837-2⟩. ⟨hal-01083038⟩