GCM SIMULATION OF THE SAHEL 1984 DROUGHT WITH ALTERNATIVE SPECIFICATIONS OF OBSERVED SST

Two climate simulations using the NASA/Goddard Institute for Space Studies coarse-resolution GCM are compared in order to investigate the sensitivity of modelled summer precipitation over West Africa to the specification of observed sea-surface temperatures (SST). Both experiments used analyses of observed SST for the boreal spring and summer of 1984, but one was derived from NOAA publications while the second came from COADS archives. Values of the NOAA SST for the tropical Atlantic were somewhat higher during June-August, leading to larger modelled evaporation rates and a model hindcast of heavy precipitation over West Africa in August, contrary to observational evidence. By comparison, dry conditions were simulated using COADS SST. The results highlight the importance of quality observations of SST and they demonstrate how sensitive the GCM is to these data.