SST variability in tropical oceans is the main driver of interannual to decadal scale climate variability in West Africa and the basis for seasonal climate prediction. Some of the biases in model simulations of climate in this region as well as forecast errors have been related to biases in SST simulation/forecast.

IRI is currently using a 2-tier system for its operational dynamical seasonal climate forecasts at global scale and exploring the advantages of allowing air-sea interactions in the forecast system by coupling the currant AGCM to either a SLAB ocean model in the tropics outside eastern Pacific where it is forced by observed or forecasted SST or to a general circulation ocean model.

This study explores the impact of such couplings on the simulation of West African monsoon in ensembles of more then 20-year simulations of uncoupled and coupled ECHAM4.5 model and hindcast experiments. The main focus is on the seasonal cycle and interannual variability (spatio-temporal patterns, teleconnexions, time-scales) of rainfall and related atmospheric variables and comparison to their counterparts in observation and reanalysis.