Preprints
https://doi.org/10.5194/wcd-2021-63
https://doi.org/10.5194/wcd-2021-63

  04 Oct 2021

04 Oct 2021

Review status: this preprint is currently under review for the journal WCD.

Strengthening tropical influence on heat generating circulation over Australia through spring

Roseanna C. McKay1,2,4, Julie M. Arblaster1,2,3, and Pandora Hope4 Roseanna C. McKay et al.
  • 1School of Earth, Atmosphere and Environment, Monash University, Victoria, Australia
  • 2Australian Research Council Centre of Excellence for Climate Extremes
  • 3National Center for Atmospheric Research, Boulder, Colorado, U.S.A.
  • 4Bureau of Meteorology, Melbourne, Victoria, Australia

Abstract. Extreme maximum temperatures during Australian spring can have deleterious impacts on a range of sectors from health to wine grapes to planning for wildfires, but are relatively understudied compared to spring rainfall. Spring maximum temperatures in Australia have been rising over recent decades, and, as such, it is important to understand how Australian spring maximum temperatures develop. Australia’s climate is influenced by variability in the tropics and extratropics, but some of this influence impacts Australia differently from winter to summer, and, consequently, may have different impacts on Australia as spring evolves. Using linear regression analysis, this paper explores the atmospheric dynamics and remote drivers of high maximum temperatures over the individual months of spring. We find that the drivers of early spring maximum temperatures in Australia are more closely related to low-level wind changes, which in turn are more related to the Southern Annular Mode than variability in the tropics. By late spring, Australia’s maximum temperatures are proportionally more related to warming through subsidence than low-level wind changes, and more closely related to tropical variability. This increased relationship with the tropical variability is linked with the breakdown of the subtropical jet through spring and an associated change in tropically-forced Rossby wave teleconnections. However, much of the maximum temperature variability cannot be explained by either tropical or extratropical variability. An improved understanding of how the extratropics and tropics projects onto the mechanisms that drive high maximum temperatures through spring may lead to improved sub-seasonal prediction of high temperatures in the future.

Roseanna C. McKay et al.

Status: open (until 20 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Roseanna C. McKay et al.

Roseanna C. McKay et al.

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Short summary
It is important to understand what makes it hot in Australia in spring so that we can be better prepared to deal with harmful impacts. We look at how the higher latitudes and tropics change the atmospheric circulation in early to late spring, and how that changes maximum temperatures in Australia. We find that the relationship between maximum temperatures and the tropics is stronger in late spring than early spring. These findings could help improve forecasts of hot months in Australia in spring.