Mean airstreams of Australia

Streamline analyses of mean monthly resultant surface winds over Australia are presented. Mean confluences represent either cyclone trajectories, or modal fronts. These analyses suggest that Australia's annual airstream climate is of two regimes: that of September to March inclusive, and April to August inclusive. The winter half-year is exemplified by a continental airstream source in southern Australia which diverges over virtually the entire continent. It continues into September and October, although dominating only the southern third to half of Australia, and is absent from November to March. During the summer half-year a new pattern emerges, with three maritime air stream sources represented over the continent: first, air from the Southern Ocean penetrates the south coast reaching its furthest northward extension from December to March inclusive; a second source originating over the Pacific Ocean dominates eastern and northern Australia; and a monsoon source originating over the Indian Ocean which flows overland affecting northern Western Australia. Two modal confluences are noted, one over northwestern Australia from November-February separating monsoon flow from that emanating from the east, and another extending from the west central coast east-southeastward to the southeast coast from November-March separating Southern Ocean air from that originating over the Pacific Ocean.