Dieppois B., Diedhiou Arona, Durand A., Fournier M., Massei N., Sebag David, Xue Y., Fontaine B. (2013). Quasi-decadal signals of Sahel rainfall and West African monsoon since the mid-twentieth century. Journal of Geophysical Research.Atmospheres, 118 (22), p. 12,587-12,599. ISSN 2169-8996.
Titre du document
Quasi-decadal signals of Sahel rainfall and West African monsoon since the mid-twentieth century
Année de publication
2013
Auteurs
Dieppois B., Diedhiou Arona, Durand A., Fournier M., Massei N., Sebag David, Xue Y., Fontaine B.
Source
Journal of Geophysical Research.Atmospheres, 2013,
118 (22), p. 12,587-12,599 ISSN 2169-8996
Sahel rainfall shows pronounced decadal variability and a negative trend between wet conditions in the 1950s1960s and dry ones in the 1970s1980s. Using continuous wavelet transform, the quasi-decadal variability (QDV) of rainfall reveals zonal contrasts. The highest QDV is identified in the 1950s1960s over western Sahel and in the 1970s1980s over eastern Sahel. The quasi-decadal atmospheric anomalies have been reconstructed using Fourier transform for the 1950s1960s and the 1970s1980s, respectively, and assessed by the composite analysis of the QDV phases for the periods before and after 1968. Over western Sahel, the rainfall QDV in the 1950s1960s is related to the North Atlantic sea surface temperature (SST) variability, as highlighted by the wavelet coherence. A southward shift trend of the Intertropical Convergence Zone (ITCZ) is identified through an enhancement of northeasterly fluxes and moisture convergence over the western part of West Africa. A decrease (increase) of southern (northern) subtropical sinking motions seems to be involved. In the 1970s1980s, a strengthening of cross-equatorial Atlantic SST and pressure gradients is related to an increase of monsoon flow from lower troposphere up to the midtroposphere and to the northward shift of the ITCZ, mainly over eastern Sahel. The Pacific SST influence is also identified, which involves changes in the global zonal circulation.
Plan de classement
Analyse, évolution des climats [021CLIMAT01]
;
Répartition spatio-temporelle des précipitations [062MECEAU01]
Descripteurs
PRECIPITATION ; VARIATION SPATIALE ; VARIATION TEMPORELLE ; TEMPERATURE DE SURFACE ; INTERACTION OCEAN ATMOSPHERE ; HUMIDITE DE L'AIR ; CIRCULATION ATMOSPHERIQUE ; METHODOLOGIE ; ANALYSE STATISTIQUE ; CHANGEMENT CLIMATIQUE ; MOUSSON ; SERIE CHRONOLOGIQUE
Description Géographique
AFRIQUE DE L'OUEST ; ZONE SAHELIENNE
Localisation
Fonds IRD [F B010060260]
Identifiant IRD
fdi:010060260
