VARIATIONS IN THE HIGH TROPOSPHERIC MEAN FLOW OVER AUSTRALIA AND NEW ZEALAND

Abstract

As first step in an investigation of changes in the high-level circulation of the southern hemisphere, more than 18,000 radiosonde flights have been used to construct a three-year series of monthly mean cross-sections for the eastern Australian sector and to draw, with their help, monthly mean 200-millibar charts for the entire region of Australia and New Zealand, by methods suited to its sparse upper-air station network. For eleven of the 36 months, the cross sections could be extended as far as the Antarctic coast to show details of a high-latitude jet stream. The 200-mb charts reveal distinct deviations from zonal flow, but only a few of these seem clearly linked to certain seasons or regions. Transitions from summer to winter flow-patterns occurred as a rule abruptly, and on several occasions coincided with the opposite transition in the zonal mean flow of the northern hemisphere.