The Association of Australian Winter Climate with Ocean Temperatures to the West

Two general circulation model experiments have been conducted with a view toward determining the sensitivity of Australian winter circulation and precipitation to the imposition of idealized sea surface temperature anomalies around the western half of Australia. In the first, a positive anomaly was imposed to the northwest of the continent and a negative anomaly to the southwest, while in the second this pattern was reversed. In the former, major changes were simulated in the circulation over the Australian sector, and significant precipitation increases were induced over more than half of the continent. By contrast, the responses to the forcing in the latter experiment were considerably less, particularly for precipitation over the continent, which showed virtually no change of significance. The results, taken in concert with those of Simmonds, suggest the important role played by warm ocean temperatures to the northwest of Australia in influencing winter rainfall. The results suggest that the addition of negative ocean temperature anomalies in the extratropics just to the west of Australia serves to strengthen the response over Australia over and above that induced by the warming of the ocean in the northwest. This is consistent with the results of analyses undertaken with the COADS data, which suggested that an even greater strengthening would be induced by a westward shift of the negative anomaly.