Trends in synoptic circulation and precipitation in the Snowy Mountains region, Australia, in the period 1958–2012

Abstract

The hydroclimate of the Snowy Mountains, south-east Australia (SEA), is influenced by tropical and extra-tropical synoptic scale weather systems. Accordingly, it is sensitive to any changes in the mid-latitude westerly wind belt, the dominant driver of precipitation in winter, and the entrainment of moisture from tropical latitudes, particularly during the warmer months of the austral summer.The region has historically observed a cool-season (April -October) dominated precipitation regime. However, evidence is presented of a decline in precipitation during the autumn and spring transition months. Autumn precipitation is particularly important for crop sowing and agricultural production in the Murray-Darling Basin downstream of the Snowy Mountains, while spring precipitation influences snowmelt and water storage replenishment in the Snowy Mountains. Instead, we show a change in the annual precipitation distribution is evident, with an increase in precipitation during warmer months.Trend analyses for the period 1958 -2012 show a decrease in annual frequency of precipitation days capable of generating inflows to the catchments of the Snowy Mountains of -1.4 days per decade on average, whilst the precipitation they generate has increased by +5.7 mm per decade. These results align with climate change projections that precipitation events are becoming less frequent but more intense.

Evidence of increased tropical moisture in southeast Australian alpine precipitation during ENSO

“…This is consistent with increases in intense precipitation during El Niño events in western North America in a warming climate [Zhou et al, 2014] and has resulted in earlier snowmelt and a decline in the proportion of snowfall in Utah [Gillies et al, 2012]. Similarly, more intense precipitation is consistent with trends previously described for the Snowy Mountains [Theobald et al, 2015b] and projections for SEA [Post et al, 2012]. A further consequence of a more energetic atmosphere associated with global warming [Wang et al, 2016;Cravatte et al, 2009;IPCC, 1995], this signifies impacts for regional water policy [Gillies et al, 2012], as well as socioeconomic impacts for alpine regions.…”

“…ENSO is a significant driver of precipitation variability in SEA with El Niño (La Niña) events associated with below (above) average precipitation [Gallant et al, 2012;Brown et al, 2009] risk of drought (flood), bushfire [Gallant et al, 2012], decreased snow cover [Pepler et al, 2015], and streamflow [Chiew et al, 2011]. Historically, the winter half year has been the wettest season in the Snowy Mountains; however, there is evidence that this may be changing [Theobald et al, 2015b]. The highest 7 day rainfall accumulation on record was observed between 27 February and 4 March 2012 coinciding with a strong La Niña event, with totals in excess of 400 mm causing widespread flooding [BoM, 2012].…”

Energy balance and snowmelt drivers of a marginal subalpine snowpack

“…At lower elevations and on some ablating aspects, the ephemeral class may be more applicable (Sanecki et al, ). Precipitation, snow conditions, and runoff exhibit very high inter‐ and intra‐annual variability (Chubb, Siems, & Manton, ; Nicholls, ; Pepler, Trewin, & Ganter, ; Theobald, McGowan, & Speirs, ), and, in a global context, the Australian snowpack can be considered highly marginal (Bormann et al, ).…”

“…and intra-annual variability (Chubb, Siems, & Manton, 2011;Nicholls, 2005;Pepler, Trewin, & Ganter, 2015;Theobald, McGowan, & Speirs, 2016), and, in a global context, the Australian snowpack can be considered highly marginal (Bormann et al, 2014).…”

Phenotypic plasticity and water availability: responses of alpine herb species along an elevation gradient

“…Indeed, particularly rapid rates of environmental change within alpine areas have been observed [4]. The Australian alpine region is likely to be particularly impacted because it has a small geographic area (<0.05% of the Australian continent), a limited elevation gradient of approximately 400 m above tree-line, and low summits (maximum of 2228 m.a.s.l) [5][6][7].…”