Variations in Upper Tropospheric Flow associated with the onset of the Australian Summer Monsoon

Abstract

Characteristics of the onset of the summer (northwest) monsoon in North Australia, and of the mean upper tropospheric flow in the east Indian Ocean-Australian region are discussed. The strength and steadiness of the upper flow are much less than that over Asia in the corresponding season. Nevertheless, the monsoon onset is shown to be associated with marked changes in the upper flow; in the tropics the easterlies increase, and the subtropical jetstream shifts southward abruptly.  The changes also extend to low latitudes of the Northern Hemisphere.  They appear to be the result of large-scale development rather than the movement of individual disturbances.