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

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

[1]  M. Raupach,et al.  Indian and Pacific Ocean Influences on Southeast Australian Drought and Soil Moisture , 2011 .

[2]  S. Lisson,et al.  Seasonal climate forecasts for agriculture: Towards better understanding and value , 2007 .

[3]  H. Meinke,et al.  Impacts of the Madden-Julian oscillation on Australian rainfall and circulation , 2009 .

[4]  Neville Nicholls,et al.  El Niño-southern oscillation and rainfall variability , 1988 .

[5]  M. England,et al.  Modulation of Australian Precipitation by Meridional Gradients in East Indian Ocean Sea Surface Temperature , 2009 .

[6]  K. Hennessy,et al.  Trends in rainfall indices for six Australian regions: 1910-2005 , 2007 .

[7]  A. H. Thiessen.  PRECIPITATION AVERAGES FOR LARGE AREAS , 1911 .

[8]  D. Kavetski,et al.  Reply to the comment of Cai et al. on the paper “On the recent warming in the Murray‐Darling Basin: Land surface interactions misunderstood” by Lockart et al. , 2010 .

[9]  Neville Nicholls,et al.  An extended high-quality historical rainfall dataset for Australia , 1997 .

[10]  Roger Jones,et al.  Pan‐evaporation measurements and Morton‐point potential evaporation estimates in Australia: are their trends the same? , 2009 .

[11]  M. England,et al.  What causes southeast Australia's worst droughts? , 2009 .

[12]  Neville Nicholls,et al.  Shifts in the synoptic systems influencing southwest Western Australia , 2006 .

[13]  K. Hennessy,et al.  Characteristics of Australian droughts under enhanced greenhouse conditions: Results from 14 global climate models , 2011 .

[14]  C. Priestley,et al.  On the Assessment of Surface Heat Flux and Evaporation Using Large-Scale Parameters , 1972 .

[15]  M. Raupach,et al.  Rising temperature depletes soil moisture and exacerbates severe drought conditions across southeast Australia , 2009 .

[16]  Anthony S. Kiem,et al.  Quantifying Drought Risk in a Nonstationary Climate , 2010 .

[17]  M. Roderick,et al.  Changes in Australian pan evaporation from 1970 to 2002 , 2004 .

[18]  Neil J. Holbrook,et al.  Decadal climate variability in Australia during the twentieth century , 1999 .

[19]  D. Verdon‐Kidd,et al.  Nature and causes of protracted droughts in southeast Australia: Comparison between the Federation, WWII, and Big Dry droughts , 2009 .

[20]  D. Jones,et al.  High-quality spatial climate data-sets for Australia , 2009 .

[21]  T. McMahon,et al.  El Nino/Southern Oscillation and Australian rainfall, streamflow and drought : Links and potential for forecasting , 1998 .

[22]  S. Franks,et al.  Multi‐decadal variability of flood risk , 2003 .

[23]  Michael L. Roderick,et al.  On the attribution of changing pan evaporation , 2007 .

[24]  D. Verdon‐Kidd,et al.  Towards understanding hydroclimatic change in Victoria, Australia – preliminary insights into the "Big Dry" , 2010 .

[25]  H. L. Penman.  Natural evaporation from open water, bare soil and grass , 1948, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[26]  F. I. Morton.  Operational estimates of areal evapotranspiration and their significance to the science and practice of hydrology , 1983 .

[27]  Bertrand Timbal,et al.  Does Soil Moisture Influence Climate Variability and Predictability over Australia , 2002 .

[28]  S. Franks,et al.  Multi‐decadal variability of drought risk, eastern Australia , 2004 .

[29]  J. Kalma,et al.  Hydrological implications of the Southern Oscillation: variability of the rainfall-runoff relationship , 2001 .

[30]  N. Nicholls.  The Changing Nature of Australian Droughts , 2004 .

[31]  D. Kavetski,et al.  On the recent warming in the Murray‐Darling Basin: Land surface interactions misunderstood , 2009 .

[32]  Roger Jones,et al.  Comparison of suitable drought indices for climate change impacts assessment over Australia towards resource management , 2008 .

[33]  D. Thompson,et al.  Australian Rainfall and Surface Temperature Variations Associated with the Southern Hemisphere Annular Mode , 2007 .

[34]  S. Franks,et al.  Multidecadal variability of rainfall and streamflow: Eastern Australia , 2004 .

[35]  Examination of Morton's CRAE model for estimating daily evaporation from field-sized areas , 1990 .

[36]  S. Power,et al.  Inter-decadal modulation of the impact of ENSO on Australia , 1999 .