Influence of climate variability on seasonal extremes over Australia

Abstract

[1] It is well understood that Australian climate is affected by natural climate variability such as El Niño-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Southern Annular Mode (SAM), depending on seasons and regions. However, studies on Australian climate extremes associated with natural climate variability remain limited. This study examines the observed impact of natural climate variability on inter-annual changes in seasonal extremes of rainfall and temperature over Australia during 1957-2010. We use non-stationary Generalized Extreme Value (GEV) analysis, where GEV parameters are specified as a linear function of modes of climate variability, and compare results with the case when climate variability is not considered. Results from two station-based observational data sets consistently suggest that extreme responses overall resemble mean responses to climate variability. Anomalously drier and hotter conditions occur over northeastern Australia and the southern coast during El Niño and a positive phase of the IOD in the cold seasons, while wetter and cooler conditions are observed during La Niña and a negative phase of IOD. A positive (negative) phase of the SAM brings wetter and cooler (drier and warmer) conditions over much of the eastern continent in summer. Covariation and relative importance of ENSO and the IOD as well as an inverse relationship between rainfall and daily maximum temperature are also found to hold for extremes. This suggests that teleconnection mechanisms responsible for seasonal mean variations may be at work for inter-annual changes in extremes, providing important implications for climate model evaluations and regional climate change projections.

Modelling the effect of the El Niño-Southern Oscillation on extreme spatial temperature events over Australia

“…Perkins and Alexander (2013), Min et al (2013) and Alexander and Arblaster (2009) have explored the effect of ENSO on the distribution of annual and seasonal maxima temperatures in Australia. They fit the generalised extreme value distribution with covariates in the location and scale parameters and map return level estimates over sites to produce spatial plots.…”

Southern Australia’s Warmest October on Record: The Role of ENSO and Climate Change

“…23.1a). A subset of SAUS, the Murray-Darling basin (MDB), is also examined as it is located in the east where the ENSO relationship w it h temperature is typically stronger (e.g., Min et al 2013 (Trewin 2013). For both SAUS and the MDB, areaweighted October average maximum temperatures were calculated for each of the ALL and NAT model simulations.…”

Introduction to the special issue: historical and projected climatic changes to Australian natural hazards

“…Bushfires: High inter-annual variability of extreme fire weather is driven in part by the combined influence of ENSO and IOD (Jolly et al 2015). Heatwaves: Positive relationship with maximum temperatures during winter and spring (Min et al 2013;White et al 2013). Frost: No literature available.…”

“…Christensen et al 2013;Hartmann et al 2013) Bushfires: Shifts in SAM combined with shifts in larger scale drivers contribute to rainfall decreases across southern Australia, which directly and indirectly affect the moisture content of bushfire fuels (Hendon et al 2014;O'Donnell et al 2015) Heatwaves: Likelihood of extreme temperatures increases during negative phases (Marshall et al 2013;Min et al 2013); relationships with summertime heatwaves are less clear . Frost: During SAM positive phases, a poleward contraction of the mid-latitude storm track resulting in drier more stable atmospheric conditions interspersed by anomalous cold air advection from the poles during anomalously strong ridging high pressure activity (Cai and Cowan 2006;Frederiksen and Frederiksen 2007;Hope et al 2006;Risbey et al 2009a).…”

“…Bushfires: El Niño is associated with hotter, drier conditions and increased bushfire risk (Harris et al 2014;Verdon et al 2004a;Williams and Karoly 1999). Heatwaves: El Niño is associated with increased frequency, intensity and duration of heatwaves in northeast Australia (Arblaster and Alexander 2012;Min et al 2013;Perkins et al 2015), yet different relationships in the far southeast (Boschat et al 2015;Parker et al 2014). Frost: El Niño is associated with an increased incidence of frost events due to drier soil Climatic Change (2016) 139:1-19 Projected changes in the ocean/atmospheric process (up to 2100) with respect to late 20th century, as reported by the IPCC Fifth Assessment Report (e.g.…”