Variability and predictability of West African droughts: a review on the role of sea surface temperature anomalies.

Belén Rodríguez-Fonseca (1, 2) , Elsa Mohino (1) , Carlos R. Mechoso (3) , Cyril Caminade (4) , Michela Biasutti (5) , Marco Gaetani (6) , Javier García-Serrano (7) , Edward K. Vizy (8) , Kerry Cook (8) , Yongkang Xue (3) , Irene Polo (9) , Teresa Losada (10) , Leonard Druyan (11) , Bernard Fontaine (12) , Juergen Bader (13) , Francisco J. Doblas-Reyes (14) , Lisa Goddard (15) , Serge Janicot (16) , Alberto Arribas (17) , William Lau (18) , Andrew Colman (17) , M. Vellinga (17) , David P. Rowell (17) , Fred Kucharski (19) , Aurore Voldoire (20)

1 Departamento de Fisica de la Tierra, Astronomía y Astrofísica [Madrid]
2 Instituto de Geociencias
3 AOS - Department of Atmospheric and Oceanic Sciences [Los Angeles]
4 School of Environmental Sciences
5 LDEO - Lamont-Doherty Earth Observatory
6 IBIMET - Istituto di Biometeorologia [Roma]
7 Institut Català de Ciències del Clima
8 Department of Geological Sciences [Austin]
9 NCAS-Climate [Reading]
10 ICAM - Instituto de Ciencias Ambientales [Toledo]
11 CCSR - Center for Climate Systems Research [New York]
12 BGS - Biogéosciences [UMR 6282]
13 MPI-M - Max Planck Institute for Meteorology
14 Institut Català de Ciències del Clima
15 IRI - International Research Institute for Climate and Society
16 PARVATI - Processus de la variabilité climatique tropicale et impacts
17 MOHC - Met Office Hadley Centre
18 GSFC Laboratory for Atmospheres
19 ICTP - Abdus Salam International Centre for Theoretical Physics [Trieste]
20 CNRM - Centre national de recherches météorologiques

The Sahel experienced a severe drought during the 1970s and 1980s after wet periods in the 1950s and 1960s. Although rainfall partiallyrecovered since the 1990s, the drought had devastating impacts on society. Most studies agree that this dry period resulted primarily fromremote effects of sea surface temperature (SST) anomalies amplified by local land surface–atmosphere interactions. This paper reviewsadvances made during the last decade to better understand the impact of global SST variability on West African rainfall at interannual todecadal time scales. At interannual time scales, a warming of the equatorial Atlantic and Pacific/Indian Oceans results in rainfall reductionover the Sahel, and positive SST anomalies over the Mediterranean Sea tend to be associated with increased rainfall. At decadal timescales, warming over the tropics leads to drought over the Sahel, whereas warming over the North Atlantic promotes increased rainfall.Prediction systems have evolved from seasonal to decadal forecasting. The agreement among future projections has improved fromCMIP3 to CMIP5, with a general tendency for slightly wetter conditions over the central part of the Sahel, drier conditions over thewestern part, and a delay in the monsoon onset. The role of the Indian Ocean, the stationarity of teleconnections, the determination of theleader ocean basin in driving decadal variability, the anthropogenic role, the reduction of the model rainfall spread, and the improvement ofsome model components are among the most important remaining questions that continue to be the focus of current international projects.

Domaines: Climatologie

Belén Rodríguez-Fonseca, Elsa Mohino, Carlos R. Mechoso, Cyril Caminade, Michela Biasutti, et al.. Variability and predictability of West African droughts: a review on the role of sea surface temperature anomalies.. Journal of Climate, 2015, 28 (10), pp.4034-4060. ⟨10.1175/JCLI-D-14-00130.1⟩. ⟨hal-01228751⟩