Links between the Big Dry in Australia and hemispheric multi-decadal climate variability – implications for water resource management

Abstract

Abstract. Southeast Australia (SEA) experienced a protracted drought during the mid-1990s until early 2010 (known as the Big Dry or Millennium Drought) that resulted in serious environmental, social and economic effects. This paper analyses a range of historical climate data sets to place the recent drought into context in terms of Southern Hemisphere inter-annual to multi-decadal hydroclimatic variability. The findings indicate that the recent Big Dry in SEA is in fact linked to the widespread Southern Hemisphere climate shift towards drier conditions that began in the mid-1970s. However, it is shown that this link is masked because the large-scale climate drivers responsible for drying in other regions of the mid-latitudes since the mid-1970s did not have the same effect on SEA during the mid-to late 1980s and early 1990s. More specifically, smaller-scale synoptic processes resulted in elevated autumn and winter rainfall (a crucial period for SEA hydrology) during the mid-to late 1980s and early 1990s, which punctuated the longer-term drying. From the mid-1990s to 2010 the frequency of the synoptic processes associated with elevated autumn/winter rainfall decreased, resulting in a return to drier than average conditions and the onset of the Big Dry. The findings presented in this paper have marked implications for water management and climate attribution studies in SEA, in particular for understanding and dealing with "baseline" (i.e. current) hydroclimatic risks.

Sources and pathways of dust during the Australian “Millennium Drought” decade

“…The Red Dawn event was the largest in a decade of heightened dust activity which was associated with a prolonged period of drought in Australia, known as the Millennium Drought [Verdon-Kidd and Kiem, 2009;Ummenhofer et al, 2009;Mitchell et al, 2010;Cai et al, 2014;O'Loingsigh et al, 2015a]. While in terms of long-term rainfall deficit the Millennium Drought persisted from 1997 to 2010 [Timbal and Fawcett, 2013;Verdon-Kidd et al, 2014], meteorological observation records indicate that the period of enhanced dust activity had a later onset and occurred between 2000[O'Loingsigh et al, 2015a. The majority of research undertaken on the Australian dust events during the Millennium Drought has tended to focus on particular aspects of individual dust storms that occurred within the decade [e.g., McGowan and Clark, 2008b].…”

Different atmospheric moisture divergence responses to extreme and moderate El Niños

“…Introduced into the geography community in the 1990s, it has been more commonly used for determining synoptic circulation patterns and downscaling Crane 1994, 2002;Crane and Hewitson 1998;Reusch et al 2007;Verdon-Kidd and Kiem 2009;Verdon-Kidd et al 2014). Here, we explore its potential applications in large scale climatic analysis.…”

Drivers of trends in Australian canola productivity and future prospects

“…2). During the subsequent millennium drought period from 1998 to 2010 (Verdon-Kidd et al 2014), the area stabilised at around 1 M ha, and in the period 1998 to 2014 average yields steadily returned to the levels achieved in 1999. The linear yield trend during the 16-year period 1998-2014 was 34 kg/ha.year or 2.0% pa based on 2014 yields, but in this case coincided with an increase in the area grown (Fig.…”

“…During its rapid expansion in the late 1990s canola had extended away from the traditional, more reliable rainfall areas (annual rainfall > 450 mm) and into lower rainfall areas (<325 mm) especially in Western Australia, and in some cases onto less suitable soils. The period from 1998 to 2010, now known in Australia as the millennium drought (Verdon-Kidd et al 2014) was characterised by dry autumns, late planting rains and limited soil water storage, together with hot, dry springs which favoured cereals such as wheat and barley over canola. As the area of canola declined and the crop retreated to the more reliable rainfall areas, the overall yield levels were maintained, except for the notable drought years of 2002 and2006 (Fig.…”

“…However, since then emerging changes in the areas, climatic conditions and farming systems in which canola is grown require ongoing adaptation to increase productivity. Emerging issues include the development of winter types and winter-spring intermediate types adapted to higher rainfall zones (Riffkin et al 2012(Riffkin et al , 2016Christy et al 2013;Sprague et al 2015), improved adaptation in the more marginal, drought/heatprone low rainfall areas with earlier flowering and maturity (Cowling 2007;Zhang et al 2013), along with changing climatic conditions in the traditional canola-growing areas during the millennium drought (Verdon-Kidd et al 2014). This has seen sowing dates moved earlier, with often unexpected and unpredictable flowering responses in current varieties developed for later sowing, leading to significant yield penalties (Brill et al 2015).…”