hide
Free keywords:
-
Abstract:
The Sahel experienced a severe drought during the 1970s and 1980s after
wet periods in the 1950s and 1960s. Although rainfall partially
recovered since the 1990s, the drought had devastating impacts on
society. Most studies agree that this dry period resulted primarily from
remote effects of sea surface temperature (SST) anomalies amplified by
local land surface-atmosphere interactions. This paper reviews advances
made during the last decade to better understand the impact of global
SST variability on West African rainfall at interannual to decadal time
scales. At interannual time scales, a warming of the equatorial Atlantic
and Pacific/Indian Oceans results in rainfall reduction over the Sahel,
and positive SST anomalies over the Mediterranean Sea tend to be
associated with increased rainfall. At decadal time scales, 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 from CMIP3 to CMIP5, with a general tendency
for slightly wetter conditions over the central part of the Sahel, drier
conditions over the western part, and a delay in the monsoon onset. The
role of the Indian Ocean, the stationarity of teleconnections, the
determination of the leader ocean basin in driving decadal variability,
the anthropogenic role, the reduction of the model rainfall spread, and
the improvement of some model components are among the most important
remaining questions that continue to be the focus of current international projects.
