Sources of Sahelian Sudan moisture: insights from a moisture-tracing atmospheric model
(English)Manuscript (preprint) (Other academic)
The summer rainfall across Sahelian Sudan is one of the main sources of water for agriculture, human and animal needs. However, the rainfall is characterized by large interannual variability, which has attracted extensive scientific effort to understand it. This study attempts to identify the source regions that contribute to Sahelian Sudan moisture budget during the monsoon months – July through September. We have used an atmospheric general circulation model with embedded water-tracing module (CAM3), forced by observed (1979-2013) sea-surface temperatures (SST). The result suggests that about 38.6% of the moisture comes with the atmospheric flow associated with the seasonal migration of the Intertropical convergence zone (ITCZ), which originates from Guinea Coast, Central Africa and the Western Sahel. The Mediterranean, Arabian Peninsula, and South Indian Ocean regions accounts for 10.2%, 8.1%, and 6.4%, respectively. Local evaporation and the rest of the globe supply the region with 20.3% and 13.2%, respectively. We also compared the result from this study to previous analysis that used the Lagrangian model FLEXPART. The two approaches differ when comparing individual regions, but are in better agreement when neighboring regions of similar atmospheric flow features are grouped together. Interannual variability of the rainfall over the region is highly correlated with contribution from regions that are associated with the ITCZ movement, which is linked to the Atlantic Multidecadal Oscillation (AMO). A dry regime during the time period 1979-1994 seems to be associated with the cold phase of AMO, and relatively wet period 1995-2013 is associated with the warm mode phase of AMO.
Sahel, Sudan, rainfall, moisture sources, moisture tagging, moisture transport
Meteorology and Atmospheric Sciences
Research subject Atmospheric Sciences and Oceanography
IdentifiersURN: urn:nbn:se:su:diva-122712OAI: oai:DiVA.org:su-122712DiVA: diva2:868279