Synoptic to large‐scale drivers of minimum temperature variability in Australia – long‐term changes

Abstract

This study documents the importance, and changes in the importance, of a suite of synoptic to large‐scale drivers of minimum temperature variability across the Australian region. The drivers investigated are the El Niño – Southern Oscillation (ENSO) as measured by the Southern Oscillation Index, atmospheric blocking, the Southern Annular Mode, and the position and intensity of the subtropical ridge. In most regions, individual drivers generally account for between about 5 and 10% of the interannual variability across Australia, although in some seasons and regions these drivers can collectively account for more than 60% of the observed variability. The amount of minimum temperature variance explained by individual drivers is highest in south‐eastern Australia in summer (December–February), where the drivers collectively account for 67% of the variance, due primarily to the relationships with blocking and ENSO. The varying importance of the drivers of minimum temperature variability between seasons and between two discrete periods (i.e. 1960–1984 and 1985–2015) has been investigated. In the more recent period the intensity of the subtropical ridge has played a more important role in minimum temperature variability, particularly in the south‐western and south‐eastern parts of Australia in summer (December–February), with the position of the subtropical ridge a feature of greater importance over much of Victoria in spring (September–November). For the more recent period the intensity of the subtropical ridge and the southern annular mode have been more important drivers of minimum temperature variability for autumn (March–May) and winter (June–August), respectively, across southern New South Wales and northern Victoria.

Evaluation of Climate Change Impact on Extreme Temperature Variability in the Blue Nile Basin, Ethiopia

“…The gross increase in the observed annual temperature is attributed to the increase in the minimum temperature. Many researchers have reported that the minimum temperature rises more than the maximum (Bayramzadeh et al, 2018, Crimp et al, 2018, Gross et al, 2018, Scott et al, 2017 The minimum temperature incremental increase is more evident than that of the maximum. The results are of good agreement with the results by (Asfaw et al, 2018).…”

Australian sub‐regional temperature responses to volcanic forcing: A critical analysis using CMIP5 models

“…Australia, bounded by the Indian, South Pacific and Southern Oceans, lies between 10°S and 44°S latitude, and 112°E and 154°E longitude. Strongest drivers of temperature variability over the continent include the El Niño Southern Oscillation (ENSO) (Trenberth, 1997; Power et al ., 1999), the Southern Annular Mode (SAM), atmospheric blocking, and the subtropical ridge (Fierro and Leslie, 2014; Crimp et al ., 2018). Southwestern and southern regions of Australia are impacted by mid‐latitude cyclones (westerly waves; cold fronts), affecting southern parts of Australia year round.…”

“…The SAM, which dominates SH circulation as a whole, significantly affects Australian climate as the position of the westerlies changes (Rogers and van Loon, 1982; Marshall, 2003; Meneghini et al ., 2007). During a positive SAM, westerlies intensify and contract towards the poles, allowing easterly winds from the Tasman Sea to move over southern Australia (Hendon et al ., 2007; Crimp et al ., 2018). A positive SAM causes significant cooling and wet conditions over most of Australia (Gillett et al ., 2006).…”

“…A positive SAM causes significant cooling and wet conditions over most of Australia (Gillett et al ., 2006). During a negative SAM, westerly winds tend to shift equatorward, and thus more strongly impact Australian weather and climate, resulting in stronger storms and frontal systems reaching further inland (Crimp et al ., 2018). Atmospheric blocking mostly occurs in the mid‐latitudes over the Tasman Sea and the southwestern Pacific.…”

“…1. identify and compare Australian sub-regional temperature responses to three relatively recent and major tropical volcanic eruptions (i.e., Krakatau, 1883;Santa Maria, 1902;Pinatubo, 1991) (Trenberth, 1997;Power et al, 1999), the Southern Annular Mode (SAM), atmospheric blocking, and the subtropical ridge (Fierro and Leslie, 2014;Crimp et al, 2018). Southwestern and southern regions of Australia are impacted by mid-latitude cyclones (westerly waves; cold fronts), affecting southern parts of Australia year round.…”