Exploring atmospheric circulation leading to three anomalous Australian spring heat events

McKay, Roseanna C.; Arblaster, Julie M.; Hope, Pandora; Lim, Eun‐Pa

doi:10.1007/s00382-020-05580-0

Cited by 10 publications

(11 citation statements)

References 60 publications

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“…Barotropic cyclones appear to the southwest and southeast of Australia, occurring in both the lower-and upper-level circulation regressions (Fig. 1a-b) and noted during recent extreme spring heat events (Gallant and Lewis, 2016;Hope et al, 2016;McKay et al, 2021). Weak anticyclonic low-level winds are found over Australia, as well as sinking motion across the eastern half of the continent.…”

Section: Spring-season Maximum Temperatures -Circulation Patterns and Associations With Driversmentioning

confidence: 93%

“…Anomalously high geopotential height (or, synonymously, anticyclonic vorticity) over southern Australia is associated with spring high maximum temperatures in Australia (Hope et al, 2015;Gallant and Lewis 2016;McKay et al, 2021). While ENSO, the IOD, and the tropical TPI also promote anomalously high geopotential height, it forms further to the south of Australia (e.g.…”

Section: Risbey Et Al 2009amentioning

confidence: 99%

“…Alexander and Arblaster, 2009). Several recent springs have already exceeded historic temperature records, with some spring months breaking records that were set only the previous year (Arblaster et al, 2014;Gallant and Lewis, 2016;Hope et al, 2015;McKay et al, 2021). Much of this observed anomalous heat has been attributed to the background global warming trend (Arblaster et al, 2014;Gallant and Lewis, 2016;Hope et al, 2015;Hope et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…The mechanisms and atmospheric circulation patterns associated with heat and connections to remote drivers may also vary through spring. McKay et al (2021) noted that the relationship with the southern Australian upper-anticyclone and maximum temperature is weaker in September than November, and suggested that the anticyclone had greater influence from the tropics in later spring. The impact of SAM in the extratropics on Australia's temperature reverses from winter to spring (Hendon et al, 2007;Risbey et al, 2009a;Marshall et al, 2012;Min et al, 2013;Hendon et al, 2014;Fogt et al, 2020) as the mean zonal winds change with the seasons (Hendon et al 2007) and the Indo-Pacific subtropical jet (STJ) weakens (Bals-Elsholz et al, 2001;Koch et al, 2006;Ceppi andHartmann, 2013, Gillett et al, 2021) so that a negative SAM phase enhances subsidence over subtropical Australia into the warmer months (Hendon et al, 2014).…”

mentioning

confidence: 99%

“…In spring, the STJ weakens sufficiently to allow for direct Rossby wave propagation from the tropical Indian Ocean. However, McKay et al (2021) suggested that 4 https://doi.org/10.5194/wcd-2021-63 Preprint. Discussion started: 4 October 2021 c Author(s) 2021.…”

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confidence: 99%

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Strengthening tropical influence on heat generating circulation over Australia through spring

McKay

Arblaster

Hope

2021

Preprint

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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.

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Section: Spring-season Maximum Temperatures -Circulation Patterns and Associations With Driversmentioning

confidence: 93%

Section: Risbey Et Al 2009amentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Strengthening tropical influence on heat generating circulation over Australia through spring

McKay

Arblaster

Hope

2021

Preprint

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Biases in the thermodynamic structure over the Southern Ocean in ERA5 and their radiative implications

Truong

Huang

Siems

et al. 2022

Intl Journal of Climatology

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The thermodynamic structure of the lower troposphere in the 37 standard levels ERA5 reanalysis has been evaluated against 2,186 high‐resolution upper air soundings collected over the Southern Ocean (SO). The reanalysis, which incorporated these soundings, was found to be skilled in depicting the general synoptic meteorology and thermodynamic structure as defined by the cluster analysis of Truong et al. (2020) Journal of Geophysical Research: Atmospheres, 125, e2020JD033214. Using dew‐point depression as a proxy for cloud, however, we found a significant reduction in the number of inferred cloud layers, which is inherited from a bias in the specific humidity in the ERA5 reanalysis, most notably over the high latitudes of the SO, where a multilayer cloud structure is frequently observed. The reanalysis was also found to have thinner inferred cloud geometric layer and shallower cloud top heights. Further analysis showed that the reanalysis displays a greater percentage of soundings having no inversion with this bias being more pronounced at high latitudes that tends to be associated with the colder sea surface temperature. While the statistics of the main inversion height are largely consistent, the average inversion strength in the ERA5 reanalysis is found to be weaker than the observations. We anticipate the 137‐level ERA5 reanalysis simulation yields a smoothed vertical structure, from which the 37 standard levels ERA5 reanalysis is linearly interpolated. An examination of the sensitivity of the radiative transfer to cloud macrophysics suggests that the correct representation of thin multiple cloud layers can help reduce the amount of downward shortwave surface radiation over the SO.

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Differences in Variations of Long-Lived and Short-Lived Summer Heat Waves during 1981–2020 over Eastern China and Their Corresponding Large-Scale Circulation Anomalies

Ji,

Chen

2024

J Meteorol Res

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Exploring atmospheric circulation leading to three anomalous Australian spring heat events

Cited by 10 publications

References 60 publications

Strengthening tropical influence on heat generating circulation over Australia through spring

Strengthening tropical influence on heat generating circulation over Australia through spring

Biases in the thermodynamic structure over the Southern Ocean in ERA5 and their radiative implications

Differences in Variations of Long-Lived and Short-Lived Summer Heat Waves during 1981–2020 over Eastern China and Their Corresponding Large-Scale Circulation Anomalies

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