Abstract
Southeastern Australia (SEA) has suffered from 10 years of low rainfall from 1997 to 2006. A protracted dry spell of this severity has been recorded once before during the 20th century, but current drought conditions are exacerbated by increasing temperatures. Impacts of this dry decade are wide-ranging, so a major research effort is being directed to better understand the region’s recent climate, its variability DQGFOLPDWHFKDQJH /DUJH VFDOHIDFWRUVWKDWLQÀXHQFHWKHFOLPDWHRIVRXWKHDVWHUQSDUWRI$XVWUDOLDLQFOXGH the El Niño – Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). This paper explores rainfall variability and trends within the State of South East Australia over the past century. For much of the State experiences large variations in rainfall over space as well as over time. We use the centre of action approach for the study of wintertime rainfall variability over the mentioned region, taking into account variations in Indian Ocean High pressure system. It is also found that east-west VKLIWVLQWKHSRVLWLRQRIWKLVVXEWURSLFDO ,QGLDQ2FHDQKLJKVLJQL¿FDQWO\LQÀXHQFHZLQWHU UDLQIDOOLQ6RXWK East Australia. The negative correlation implies that when the Indian High shifted to the east there is less rainfall over south east Australia. Similarly when the Indian Ocean High Pressure maximum there is less rainfall observed and vice versa. It indicates that the Indian High pressure in the winter has steadily increased and expanded since the 1950s which is the most direct explanation of the drying trend over the South East Australia. (IOHP and IOHLN) explain 22% variability of rainfall over SEA. Our calculations suggest the YDULDELOLW\RIZLQWHUSUHFLSLWDWLRQRYHU6RXWK(DVW$XVWUDOLDLVQRWRQO\LQÀXHQFHGE\WKHLQWHQVLW\RI,QGLDQ Ocean High pressure system but it also depends on its zonal movement.
