Modes of climate variability and heat waves in Victoria, southeastern Australia

Abstract

Summertime heat waves in the southeastern state of Victoria, Australia, are associated with broad anticyclonic upper level potential vorticity (PV) anomalies. The current research establishes the relationship between heat waves, precipitation, and three modes of climate variability of importance for rainfall in Australia: the El Niño-Southern Oscillation (ENSO), Madden-Julian Oscillation (MJO), and Southern Annular Mode (SAM). Heat waves in Victoria in summer are more common during phases 3-6 of the MJO (when convection is enhanced over the eastern Indian Ocean, Maritime Continent, and western Pacific Ocean) and La Niña phases of ENSO. The PV-Theta (Θ) structure of the heat wave and pattern of convection varies with the phase of each mode of variability. Enhanced tropical convection results in a heat wave characterized by a monopole of anticyclonic PV, whereas suppressed convection is associated with a dipole of anticyclonic and cyclonic PV.

Relationships between climate variability, soil moisture, and Australian heatwaves

“…These sea level high-pressure systems are coupled with high-pressure anomalies aloft [e.g., Meehl and Tebaldi, 2004;Trigo et al, 2005;Dole et al, 2011] and are stationary for an extended number of days [e.g., Nairn and Fawcett, 2013]. Dynamical teleconnections of prevailing heatwave weather systems to tropical low-pressure systems and Rossby waves also exist [Parker et al, 2013[Parker et al, , 2014aBoschat et al, 2015] and may be more prevalent during particular modes of climate variability [Parker et al, 2014b]. Indeed, climate variability modes are another link in the heatwave development chain; however, with the exception of some focus over southeast Australia [Parker et al, 2014a[Parker et al, , 2014b, little research has been undertaken regarding continental-scale relationships between these phenomena and discrete heatwave characteristics.…”

“…Dynamical teleconnections of prevailing heatwave weather systems to tropical low-pressure systems and Rossby waves also exist [Parker et al, 2013[Parker et al, , 2014aBoschat et al, 2015] and may be more prevalent during particular modes of climate variability [Parker et al, 2014b]. Indeed, climate variability modes are another link in the heatwave development chain; however, with the exception of some focus over southeast Australia [Parker et al, 2014a[Parker et al, , 2014b, little research has been undertaken regarding continental-scale relationships between these phenomena and discrete heatwave characteristics. A fourth link, soil moisture, has also been identified, with results clearly indicating more intense and longer heatwaves when antecedent soil moisture conditions are particularly dry [Vautard et al, 2007;Mueller and Seneviratne, 2012;Fischer et al, 2007aFischer et al, , 2007bHoerling et al, 2013;Miralles et al, 2014].…”

“…We consider climate variability modes to have an important influence on heatwaves since they drive the background conditions in which changes to soil moisture can occur, as well as influencing the dominating synoptic systems [e.g., Alexander et al, 2002;Ummenhofer et al, 2011;Marshall et al, 2012;Parker et al, 2014b]. Furthermore, key relationships have been found between single-day temperature extremes and climate variability modes in Kenyon and Hegerl [2008], Alexander and Arblaster [2009], and Arblaster and Alexander [2012] at the global scale, as well as in Min et al [2013] over Australia.…”

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

“…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.…”

On the Relationship between Heat Waves over the Western and Central Europe and NAO, SOI, El-Nino 3.4 in Summer 2015

“…There is a several study illustrate that ENSO has a significant influence on the heat waves and climate variability in many parts of the globe, (e.g., [7] [17] and [18] [19] [20]). A heat wave is a prolonged period of excessively hot weather.…”