Skill of Sahel rainfall variability in four atmospheric GCMs forced by prescribed SST

Vincent Moron (1) , N. Philippon (2) , B. Fontaine (3)

1 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
2 CRC - Centre de Recherches de Climatologie
3 LP3 - Laboratoire Lasers, Plasmas et Procédés photoniques

The inter-annual and long-term variability of July-September regional rainfall over the central and western Sahel (16°W-20°E; 11.25°-18.75°N) is evaluated using 21 runs from four atmospheric general circulation models (AGCMs) integrated from 1948. The skill is stronger at decadal time scales: each AGCM simulates quite successfully the rainfall decrease from the wet 1950-60s toward the dry 1970-90s although its amplitude is lower than observed. At inter-annual time scales, the skill is smaller and decreases over time between the 1950-70s and the recent dry period; all AGCMs have a close to zero skill around the 1980s. This is not linked to a reduced AGCM sensivity to global SST but to their failure to reproduce the observed SST-rainfall teleconnection changes, in particular the weakening (strengthening) linear relationship with the equatorial and southern Atlantic (equatorial Pacific).

Mots clés: 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation; 3354 Meteorology and Atmospheric Dynamics: Precipitation (1854); 3374 Meteorology and Atmospheric Dynamics: Tropical meteorology. Citation: Moron; V.; N. Philippon; and B. Fontaine; Skill of Sahel rainfall variability in four atmospheric GCMs forced by prescribed SST; Geophys

Domaines: Océan, Atmosphère; Climatologie

Vincent Moron, N. Philippon, B. Fontaine. Skill of Sahel rainfall variability in four atmospheric GCMs forced by prescribed SST. Geophysical Research Letters, 2003, 30 (23), pp.n/a-n/a. ⟨10.1029/2003GL018006⟩. ⟨hal-02895214⟩