Experimental Predications of Climatic Variability for Lead Times of 12 Months

Interannual variability of present-day climate has been clearly linked to the occurrence of large-scale sea-surface temperature anomalies, particularly in the Pacific Ocean. Prediction of such anomalies many seasons in advance by using relatively simple, coupled oceanic-atmospheric models provides a basis for predicting the atmospheric climate over the same period. This is achieved by inserting the sea-surface temperature anomalies predicted by the coupled model at appropriate time intervals into a global climatic model and integrating forward in time. Prediction experiments for 1991 and 1992 have been conducted on this basis using sea-surface temperature anomalies predicted for the Pacific Ocean' Global and regional rainfall outcomes are presented here, although the predictions are not expected to be valid for the whole globe. Detailed results are given for Australia and southern Africa, which experienced severe drought conditions in 1991 and 1992. Useful skill, with statistical significance for predictions when substantial rainfall anomalies occurred, was obtained for these regions, indicating the potential utility of the method. Considerable scope exists for improvements in the technique presented here, particularly in the global climatic model used, so that increasing accuracy should result as the technique is developed. Operational implementation of this method is essentially straightforward.