Severe heat waves in Southern Australia: synoptic climatology and large scale connections

Pezza, Alexandre Bernardes; Rensch, Peter van; Cai, Wenju

doi:10.1007/s00382-011-1016-2

Cited by 173 publications

(156 citation statements)

References 28 publications

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“…This accounts for the initially counterintuitive finding of Pook et al (2006), who report significant positive correlations between days with cutoff rainfall in southeastern Australia and atmospheric blocking in the Australian sector. This role of wintertime atmospheric blocking in southeastern Australia is thus distinct from the more well-known association with summer heat waves in Australia (Hudson et al 2011;Pezza et al 2012) and Europe (e.g., Sillmann and Croci-Maspoli 2009;Coumou and Rahmstorf 2012, and references therein). Substantial decreases in cutoff low pressure rainfall over southern regions of Australia have been projected for the twenty-first century, using a regional model, linked to changes in the blocking in the Tasman Sea region and the split structure in the jet over the region (Grose et al 2012).…”

Section: Introductionmentioning

confidence: 77%

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

et al. 2013

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Characteristics of atmospheric blocking in the Southern Hemisphere (SH) are explored in atmospheric general circulation model (AGCM) simulations with the Community Atmosphere Model, version 3, with a particular focus on the Australia-New Zealand sector. Preferred locations of blocking in SH observations and the associated seasonal cycle are well represented in the AGCM simulations, but the observed magnitude of blocking is underestimated throughout the year, particularly in late winter and spring. This is related to overly zonal flow due to an enhanced meridional pressure gradient in the model, which results in a decreased amplitude of the longwave trough/ridge pattern. A range of AGCM sensitivity experiments explores the effect on SH blocking of tropical heating, midlatitude sea surface temperatures, and land-sea temperature gradients created over the Australian continent during austral winter. The combined effects of tropical heating and extratropical temperature gradients are further explored in a configuration that is favorable for blocking in the Australia-New Zealand sector with warm SST anomalies to the north of Australia, cold to the southwest of Australia, warm to the southeast, and cool Australian land temperatures. The blockingfavorable configuration indicates a significant strengthening of the subtropical jet and a reduction in midlatitude flow, which results from changes in the thermal wind. While these overall changes in mean climate, predominantly forced by the tropical heating, enhance blocking activity, the magnitude of atmospheric blocking compared to observations is still underestimated. The blocking-unfavorable configuration with surface forcing anomalies of opposite sign results in a weakening subtropical jet, enhanced midlatitude flow, and significantly reduced blocking.

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Section: Introductionmentioning

confidence: 77%

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

et al. 2013

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“…For this type, solar heating, static stability, and the dryness of the air mass also play fundamental roles [14]. We shall refer to this HWs/WSs type as radiative HWs/WSs type to avoid any confusion.…”

Section: Synoptic Classification Of Hws/wss In Romaniamentioning

confidence: 99%

“…Usually, when a relative threshold is used to define extreme high temperature events over the year, HWs term is employed for summer, late spring, and early winter events (May-September), while WS term is frequently used for winter, late autumn, and early spring events (October-April). They have become a very important issue as they imply a significant threat to life and property in times of accelerated population growth and climate change [14].…”

Section: Introductionmentioning

confidence: 99%

Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

et al. 2017

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Abstract:Heat waves and warm spells are extreme meteorological events that generate a significant number of casualties in temperate regions, as well as outside of temperate regions. For the purpose of this paper, heat waves and warm spells were identified based on daily maximum temperatures recorded at 27 weather stations located in Romania over a 55-year period . The intensity threshold was the 90th percentile, and the length of an event was of minimum three consecutive days. We analyzed 111 heat wave and warm spell events totaling 423 days. The classification of synoptic conditions was based on daily reanalysis at three geopotential levels and on the online version of a backward trajectories model. The main findings are that there are two major types of genetic conditions. These were identified as: (i) radiative heat waves and warm spells (type A) generated by warming the air mass due to high amounts of radiation which was found dominant in warm season; and (ii) advective heat waves and warm spells (type B) generated mainly by warm air mass advection which prevails in winter and transition seasons. These major types consist of two and three sub-types, respectively. The results could become a useful tool for weather forecasters in order to better predict the occurrence of heat waves and warm spells.

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“…For example, extreme heatwaves in southern Australia are typically induced and maintained by a blocking anticyclone that originates in the western Indian Ocean. An increased meridional SST gradient in the Indian Ocean, and hence enhanced baroclinicity, amplify upper-level Rossby waves which trigger heatwave conditions (Pezza et al, 2012). In summer 2003, warm SST anomalies in the northern Atlantic Ocean reduced the meridional SST gradient and decreased baroclinic activity, resulting in a northward shift of the polar jet and an expansion of the anticyclone and leading to an extreme heatwave over Europe (Feudale and Shukla, 2011).…”

Section: Air-sea Interactions In the Extratropicsmentioning

confidence: 99%

“…Prodhomme et al, 2014) and extratropical blocking (e.g. Pezza et al, 2012). A better understanding and simulation of how air-sea interactions influence these phenomena could improve subseasonal prediction and regional climate change projections.…”

Section: Introductionmentioning

confidence: 99%

MetUM-GOML1: a near-globally coupled atmosphere–ocean-mixed-layer model

2015

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Abstract. Well-resolved air-sea interactions are simulated in a new ocean mixed-layer, coupled configuration of the Met Office Unified Model (MetUM-GOML), comprising the MetUM coupled to the Multi-Column K Profile Parameterization ocean (MC-KPP). This is the first globally coupled system which provides a vertically resolved, high near-surface resolution ocean at comparable computational cost to running in atmosphere-only mode. As well as being computationally inexpensive, this modelling framework is adaptable -the independent MC-KPP columns can be applied selectively in space and time -and controllable -by using temperature and salinity corrections the model can be constrained to any ocean state.The framework provides a powerful research tool for process-based studies of the impact of air-sea interactions in the global climate system. MetUM simulations have been performed which separate the impact of introducing interannual variability in sea surface temperatures (SSTs) from the impact of having atmosphere-ocean feedbacks. The representation of key aspects of tropical and extratropical variability are used to assess the performance of these simulations. Coupling the MetUM to MC-KPP is shown, for example, to reduce tropical precipitation biases, improve the propagation of, and spectral power associated with, the MaddenJulian Oscillation and produce closer-to-observed patterns of springtime blocking activity over the Euro-Atlantic region.

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Severe heat waves in Southern Australia: synoptic climatology and large scale connections

Cited by 173 publications

References 28 publications

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

Impact of Surface Forcing on Southern Hemisphere Atmospheric Blocking in the Australia–New Zealand Sector

Synoptic Conditions Generating Heat Waves and Warm Spells in Romania

MetUM-GOML1: a near-globally coupled atmosphere–ocean-mixed-layer model

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