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| Titel |
Comparative influence of land and sea surfaces on the Sahelian drought: a numerical study |
| VerfasserIn |
Arona Diedhiou, Jean-Francçois Mahfouf |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 14, no. 1 ; Nr. 14, no. 1, S.115-130 |
| Datensatznummer |
250012142
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| Publikation (Nr.) |
 copernicus.org/angeo-14-115-1996.pdf |
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| Zusammenfassung |
| The aim of this work is to compare the
relative impact of land and sea surface anomalies on Sahel rainfall and to
describe the associated anomalies in the atmospheric general circulation. This
sensitivity study was done with the Météo-France climate model: ARPEGE. The
sensitivity to land surface conditions consists of changes in the management of
water and heat exchanges by vegetation cover and bare soil. The sensitivity to
ocean surfaces consists in forcing the lower boundary of the model with
worldwide composite sea surface temperature (SST) anomalies obtained from the
difference between 4 dry Sahel years and 4 wet Sahel years observed since 1970.
For each case, the spatiotemporal variability of the simulated rainfall anomaly
and changes in the modelled tropical easterly jet (TEJ) and African easterly jet
(AEJ) are discussed. The global changes in land surface evaporation have caused
a rainfall deficit over the Sahel and over the Guinea Coast. No significant
changes in the simulated TEJ and an enhancement of the AEJ are found; at the
surface, the energy budget and the hydrological cycle are substantially
modified. On the other hand, SST anomalies induce a negative rainfall anomaly
over the Sahel and a positive rainfall anomaly to the south of this area. The
rainfall deficit due to those anomalies is consistent with previous diagnostic
and sensitivity studies. The TEJ is weaker and the AEJ is stronger than in the
reference. The composite impact of SST and land surfaces anomalies is also
analyzed: the simulated rainfall anomaly is similar to the observed mean African
drought patterns. This work suggests that large-scale variations of surface
conditions may have a substantial influence on Sahel rainfall and shows the
importance of land surface parameterization in climate change modelling. In
addition, it points out the interest in accurately considering the land and sea
surfaces conditions in sensitivity studies on Sahel rainfall. |
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