The characteristics of seasonal-scale droughts in Australia, 1911–2009

Authors


A. J. E. Gallant, School of Earth Sciences, University of Melbourne, VIC 3010, Australia. E-mail: agallant@unimelb.edu.au

ABSTRACT

Climatologies and variations in seasonal-scale droughts in Australia are quantified using four indices representing the characteristics of the lower tails of rainfall and soil moisture distributions. These indices estimate variations in drought frequency, duration and intensity from 1911 to 2009 across Australia and for five large-scale regions. Since 1911, large interdecadal variations in the characteristics of seasonal-scale droughts have overlain trends towards less frequent, shorter and less severe droughts across much of Australia, with the strongest trends in northwest Australia. Regional exceptions include increases in seasonal-scale drought frequency, duration and intensity in areas of southwest and southeast Australia. In parts of the west and southeast of the Murray–Darling Basin, the average duration of seasonal-scale droughts, defined as successive seasons in drought, statistically significantly increased by between 10 and 69% during the second half of the 20th Century. Averaged across large-scale regions in southeast and northwest Australia, decades with longer-lasting and more intense soil moisture-based seasonal droughts had statistically significantly higher actual evaporation compared with other decades. These were combined with modest rainfall deficits, suggesting that evaporation may be an important process for regulating drought duration or intensity in these regions. However, other hydroclimatic processes that were not assessed here likely also influence soil moisture, making attribution difficult. Copyright © 2012 Royal Meteorological Society

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